This document is a student submission made to the Australian Medical Students’ Association Limited (AMSA). All use is subject to our Terms of Service available at https://amsa.org.au/terms-of-service

Student Submitted Resources

Gastroenterology

Gastrointestinal Medicine & Nutrition

Tarren Zimsen

James Cook University

Last Update: December 2012 | File ID: GASTR2017.02

This document is a student submission made to the Australian Medical Students’ Association Limited (AMSA). All use is subject to our Terms of Service available at https://amsa.org.au/terms-of-service

ContentsGastrointestinal Medicine and Nutrition

1 Histology of the GIT ..……………….. 6

2 Abdominal Cavity and Peritoneum ……………….. 10

3 Histology of the Biliary Tree ……………….. 16

4 GI tract motility ……………….. 21

5 Gastrointestinal secretions and absorptions ……………….. 25

6 Digestion and absorption (CHO / Protein) ……………….. 30

7 Liver digestion and absorption (liver function) ……………….. 34

8 Metabolism of the Liver ……………….. 39

9 Nutritional requirements for health ……………….. 45

10 Nutritional status assessment ……………….. 53

11 Control of food intake ……………….. 59

12 Diet and Disease Management ……………….. 66

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Study Period 2

Summary notes

2012

By Tarren Zimsen

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Gastrointestinal

Medicine and

Nutrition

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Gastrointestinal medicine and nutrition week 1 summary

Histology of the GIT

The human digestive system is effectively one long tube that contains many different subsets all

serving different purposes. As the tube is hollow in a sense, with openings in the oral cavity and the

anus, it is classified as the external environment and thus goblet cells are what secrete into it. The 4

basic layers of GI tract are similar in almost all of its organs except for a few differences.

The basic layers of the GI tract:

(i) The mucosa is the most inner layer and it comes into contact with the lumen. The

mucosa itself is further separated into 3 different layers which are the epithelia, lamina

propria and the muscularis mucosae. The epithelial lining typically has simple columnar

cells however it parts that undergo high abrasive forces stratified squamous epithelia is

also found. The epithelia layer is responsible for a lot of the mucous and enzyme

secretion. The lamina propria underlies the epithelia lining and is a layer of connective

tissue. It has the role of absorbing digested nutrience, supplying the epithelia with

nourishment and defends against bacterial attack through direct lymphatic drainage.

The last layer of the mucosa is the muscularis mucosae which controls fine movement

for example if food gets caught onto the epithelium.

(ii) The submucosa is an areolar connective tissue containing a rich supply of blood and

lymphatic vessels, lymphoid follicles and nerve fibres. The elastic fibres within it allow

the muscle to change shape and retain its elasticity.

(iii) The muscularis externa is divided

into two layers of muscle, the

circular and the longitudinal.

These two layers work together to

produce a smooth muscle

contraction that allows peristalsis.

In certain parts of the GI tract the

circular layer becomes larger to

produce a sphincter.

(iv) The serosa is the most outer layer

of the canal.

The statements that are set out in the above paragraph are general and there are sometimes big

differences. For example in the oesophagus the epithelium layer is actually stratified squamous

instead of simple columnar. This is purely due to the amount of abrasive forces that are in play in the

oesophagus. Another factor that must be noted is that in the oesophagus the skeletal, voluntary

muscle, slowly becomes smooth muscle thus meaning that the person has no control over the

digestion.

Once you get to the stomach the epithelium turns back to simple columnar cells. The stomach also

contains a large amount of goblet cells that help to secrete the enzymes into the vessel. It is the

ducts in the sub mucosa that produce the mucous that lines the stomach and ensures that it does

not undergo any self-digestion. The stomach also has three layers of muscularis externa which

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allows it to contract in varying manners. The mucosa of the stomach is full

of glands and pits, with different types of glands and pits being placed in

different areas. The length of the pits and glands change as you progress

from the cardia to the body and the pylorus. These gastric pits are useful

for secreting a lot of the HCl that is found in the stomach along with the

enzymes (the stomach releases 2L of gastric juices every day). The stomach

is separated from the oesophagus superiorly and the duodenum inferiorly

by sphincters.

In order to get maximum surface area and therefore maximum absorbance of

food the small intestines have a clever mechanism of increasing its surface area.

First the plicae circularis then the villus and finally the enterocytes all fold in on

each other to create a velvet like appearance, but more importantly increasing

the surface area to 200 sq m. The small intestines is split into three sections the

duodenum which is the closest to the stomach then the jejunum and finally the

ilium. The intestines also contain little inversions into the intestinal wall, these are known as crypts

of lieberkuhn and they carry out the task of secreting intestinal juice that can help the movement

down the digestive tract. In the duodenum specific there is a gland known as the brunners gland

which secretes an alkaline solution to help neutralise the acidic solution that is entering from the

stomach. The jejunum contains the tallest villi which allows for the most absorption. The ileum

contains a layer of cells deep to the epithelium known as lymphoid tissue that is the first line of

defence for micro-organisms that enter the body.

The large intestines are the sight of the major water reabsorption. Because of the decrease in the

fluid content large amounts of goblet cells are required to ensure that the bolus is fluid enough to

transport through. The large intestines is split up into 5 parts: the secum, accending colon,

transverse colon, descending colon and the sigmoid. Another factor that is worth noting is that the

longitudinal layer of the muscularis externa changes to become three tinea coli that helps to great

degree with faecal compaction.

Appendix is an organ that has very little use in humans however can cause great risks.

The rectum must have an even higher number of goblet cells to allow

the faeces to be excreted onto the anus. It contains rectal valves which

allow it to decipher between gas and solid in the rectum. This is crucial

for faecal control. The ano rectal junction shows a quite succinct

transition between the two, with the anus the later purely responsible

with holding the stool in, and the rectum still involved in absorption and

separating solid from gas. The anus is voluntary and the rectum

involuntary.

Rectal valves

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The regions of the abdomen

The abdomen can either be divided by the four quadrant pattern or the

nine region pattern.

The four quadrant pattern takes one section through the median plane and

one through the trans umbilical plane which separates into right upper, left

upper, right lower, and left lower. What must be noted is that it is the left

and right hand side of the patient not you.

The nine region pattern divides the body down the mid clavicular planes

which run through the middle of the clavicles. The horizontal plains run

through the intertubular plane which is roughly the height of the top of

the ilium. And the subcostal plane which is just under the last rib.

The abdominal wall

The anterior abdominal wall consists of multiple layers from the skin all

the way through to the parietal peritoneum. All these layers work

together to maintain the intra-abdominal pressure and make sure that

the organs stay where they are supposed to stay. The obvious outer layer is the skin; deep to this is

more superficial and the scarpas layer which is deeper. The Campers layer is made predominantly

made of connective tissue whereas the scarpas layer is extremely fibrous. Fat layerings are also

found in this region and thickness varies on the health status of the individual being tested. One

more layer deeper is the deep fascia which has a very large connective tissue medium (aponeurotic=

big tendon). The external oblique comes in which runs anteriorly, inferiorly, and medially. The

internal oblique is one more layer in and it runs anteriorly, superiorly and medially. These muscles

help to allow the body to turn. The next layer in is the transverses abdominus where the fibres run

more or less horizontally. The rectus abdominus run down the middle and are what are defined in a

six pack. The line down the centre of the rectus abdominus is the linea alba. Inside all the layers of

muscle there are two layers of membrane that separate the contracting muscle from the abdominal

organs. The more superficial of the two is the transversalis fascia and the deeper one is the parietal

peritoneum. There are also visce

them to be compartmentalised.

The posterior abdominal wall is also crucial in maintaining the intra-abdominal pressure. The

muscles that play a role in the posterior wall are the psoas major, the quadratus lumborum the

transersus abdominis and the iliacus.

The roof of the abdominal cavity is the diaphragm. It is the primary muscle that is involved in

breathing for the human. Its contraction and relaxation helps to create pressure differences that aid

in breathing. It is said to be a musculartendinous partition as the central tendon is surrounded by a

muscle. The tendon stretches and relaxes to allow for the expansion of the lungs. The diaphragm has

three foramens in it. The vena cava goes through one of the foramens through the tendenous part

of the diaphragm at T8. The Oesophagus goes through the muscular portion at T10 and the

diaphragm helps to create a sphincter. The last vessel that comes through the diaphragm is the

abdominal aorta which comes down the back at T12. The abdominal aorta feeds the phemoral artery

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which feeds the legs along with all other abdominal organs. There are multiple vessels that leave the

abdominal aorta and not all are symmetrical.

The lymphatic drainage of the posterior abdominal wall is described quite simply. The ciliac

mesenteric lymph nodes drain the top, then the superior mesenteric lymph nodes drain the middle

umbilicus region, and the inferior mesenteric lymph nodes drain the bottom.

The nerves that exit the spinal cord must get through the psoas major muscle and both the lumbar

plexus and femoral nerves do this.

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Gastrointestinal Medicine and Nutrition week 2 summary

Abdominal Cavity and Peritoneum

The peritoneum is a think membrane that lines

the abdominal wall. Other types of peritoneum

also line the organs in the GIT. The peritoneal

cavity which is defined by the diaphragm

superiorly and the pelvic cavity inferiorly is

divided into a greater and lesser sac. The two

sacs are continuous (joined) through the

omental foramen. The abdominal peritoneum

gains its blood supply from the vessels that

support the abdominal wall, whereas the

visceral peritoneum gains their blood supply

from the vessels that supply the individual organs. The visceral peritoneum is developed through

endocytosis like engulfment of the organs during

development. It must be noted that not all parts of the

digestive system have peritoneum and other ligaments

holding it together. Some parts are completely free to

move. The image right highlights the parts that are

attached on the left and the parts that are free moving

on the right.

Mesenteries are peritoneal folds that attach the

viscera to the posterior abdominal wall. The mesentery is associated with the small intestines; it runs

from the ilium and the jejunum junction to the duodenum jejunum junction. It contains 2 layers of

connective tissue with varying amounts of accumulated fat depending on the person. The transverse

mesocolon is associated with the transverse colon and it connects this to the posterior abdominal

wall. The double layered connective tissue leave the posterior abdominal wall near the head and

body of the pancreas and then head down to surround the transverse colon. The sigmoid mesocolon

is associated with the sigmoid colon is an inverted V shape that attaches the sigmoid colon to the

abdominal wall.

On top of these three mesenteries there are also a lot of peritoneal ligaments that attach

the organs to the abdominal wall. All these are in place to ensure that excessive movement of the

organs in the abdominal cavity does not occur. The peritoneum even folds in such a manner

sometimes to create pouches in the abdomen that other aspects cannot get to. The ligament that

runs down the middle of the liver is known as the palistone ligament.

Omenta are a 4 layered piece of

peritoneum that runs like an apron down the front

of the abdominal organs. It runs from the lower

part of the stomach to the jejunum and ilium. The

width of the omenta varies depending on the

amount of body fat stored in the individual.

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Torsion is when organ spins on an axis. This can be detrimental to the health of the organ

and the individual as the blood vessels that feed into the organ may not allow the organ to stay

alive.

The mouth: is the site of the initial digestion of the food. The digestive system in a human being is

basically a system that is tasked with disassembly. In the mouth mechanical digestion occurs through

the physical nature of the food being grinded by the teeth, and chemical digestion of the enzymes in

the salivary glands working to digest the food.

The salivary glands (p 1044 1047 Grays anatomy)

The salivary glands are important in human food digestions as they allow the chemical

digestion to occur in the mouth. They are mostly small glands in the mucosa and submucosa of the

oral epithelial lining. There are three relatively large glands known as the parotid, which is found

sublingual glands is at the base of the mouth.

Once out of the mouth the food passes through the pharynx and the thoracic oesophagus. The food

is then moved down the oesophagus through a process called peristalsis into the stomach. The

oesophagus is approximately 25 cm long and cuts through the diaphragm at vertebrae T 10. In the

oesophagus there are compressions that are present due to other vessels in the region. One

constriction is due to the presence of the aorta and the other is due to the

left main bronchus.

The stomach is the next organ in the digestive system; the lower

oesophageal sphincter stops the bolus of food from going back up the

oesophagus from the stomach after it has passed. When the sphincter fails

is divided into four parts; the cardia, the fundus, the body, and the pyloric.

The inside of the stomach contains a structure known as rugae which is

present to allow the stomach to be able to expand when large meals are consumed. In the linning of

the stomach you get mucosal folds that secrete the mucous to ensure that the pepsinogen that is

also s -digest and eat away at the stomach lining. It is the goblet cells inside these

glands that secrete the mucous, the parietal cells that secrete the HCl and the chief cells secrete the

enzyme pepsinogen which becomes pepsin in the highly acidic stomach.

The small intestines are the next organ along in the digestive tract. The small intestines have

the chief responsibility for absorption and hence they have large numbers of villi to increase the

surface area. The small intestines are linked to the stomach through the pyloric junction and as soon

as the bolus of food enters the small intestines it must be treated

by an alkaline solution to neutralise. The alkaline is secreted from

es from

mechanisms. The small intestine is split into three sections in total

equalling 6 or 7 metres.

(i) Duodenum is the first part of the small intestines, it is

quite short, and contains the highest number of plica

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intestines is also where the bile from the gall bladder and the

pancreatic juice enters.

(ii) The jejunum; is next and is often empty it has a larger wall

and more prominent plicae circularis than the ilium. It also

contains a less prominent arterial arcade and longer vasa

recta. The jejunum makes up approximately 2/5 of the small

intestines

(iii) The Ileum is the last part and makes up about 3/5 of the small

intestines. It contains very little plica circularis and this

structure is completely absent towards the end. It contains a

large number of lymphoid tissue to defend against infection. It

also contains a lot more pertinent arcade of arteries with much

shorter vasa recta

The large intestine is the next component in the digestive system. It effectively frames the small

intestines beginning from the iliocecal and ending at anus. The large intestines are around 7 cm in

diameter and plays a crucial role in absorbing water prior to faeces are created. The wall of the large

intestines must contain large amounts of goblet cells to help with the flow of bolus through the

system. The bolus would now be incredibly hard especially after the water has been taken out. There

are three characteristic features of the large intestines. firstly the tinea coli which is a muscle that

runs along it is present instead of the longitudinal layer of the muscularis externa. Secondly the

presence of haustra which are the bumpy external of the large intestines are present. This structure

is not found anywhere else and has a role to play in faecal

compaction and making faeces that particular shape. The third

is the epiploic appendages which are accumulations of a fat that

are attached to the haustra. These three features tell the

examiner whether the piece they are looking at is the small or

large intestines. The sheer fact of determining the difference

through size can sometimes be dangerous, as depending on the

time of the last meal of the deseased different areas may be

larger. The large intestine is made of seven parts: the cecum

and appendix, the ascending colon, the transverse colon, the

descending colon, the sigmoid, the rectum and the anus.

- The cecum (secum) is the first part of the large

intestines; it is joined to the ilium of the small intestines through the iliocecal valve. The

appendix opens into the cecum at the iliocecal junction.

- The role of the appendix is unknown; however it can cause enormous

amounts of discomfort if the patient gets appendicitis. It is narrow

and wormlike, with its own mesentery. It contains tinea coli that

converge at its base. The appendix can be found in varying different

orientations, sometimes even inside the cecum.

- Large Intestines: is a continuation of the cecum, it runs up the body in

the ascending colon, across the top of the small intestines in the

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transverse colon, and descends down the left hand side of the patient. The sigmoid is the

end of the colon and runs from the pelvic brim to the S3, and its S shape helps to store

faeces until defecation.

- The rectum is continuous with the sigmoid. The rectum and the anus play a crucial role in

controlling defecation. They both contain a sphincter that works in opposite ways. The inner

sphincter is involuntary and is contracted until an adequate amount of faeces builds up. At

this point the muscle relaxes letting the faeces through. The outer sphincter which is usually

relaxed must then contract. The outer sphincter is voluntary and hence people have control

of their bowel movements. The two sphincters work in opposing natures to each other.

The digestive system is divided into three distinct portions; a foregut,

midgut and a hindgut. The foregut by name is the most superior of the

three, the midgut is in the middle and the hindgut most inferior. The

foregut is made up of the liver, stomach, spleen, and pancreas, the midgut

is made of the small intestines and the ascending and transverse colon,

while the hindgut contains the descending colon, sigmoid and the rectum

and anus.

Arteries that supply the GIT

The celiac trunk that branches off the abdominal aorta, further branches

off to feed the foregut. It splits into the left gastric artery, the splenic

artery and the common hepatic artery. The other two arteries that extend

away from the abdominal aorta are the superior mesenteric artery which feeds the midgut and the

inferior mesenteric artery which feeds the hindgut.

Other information regarding vessels in the abdomen (add after SS use greys to formulate notes)

- Left Gastric Artery: supplies the abdominal oesophagus

and travels along the lesser curvature of the stomach to

supply the lesser curvature side. The left gastric artery is

the smallest of the three vessels that originate from the

cilia trunk. The left gastric artery anastomoses (joins

together to form a circle) with the right gastric artery. The

advantage of having anastomoses is that it allows the

vessels to get around clots etc.

- Splenic artery: is one of the branches of the celiac trunk. And passes over the margin of the

pancreas. The pancreoduodenal artery from the splenic artery supplies the pancreas. The

splenic artery vessel that actually feeds the spleen must

have a little slack in the vessel as the spleen that is sitting

directly under the diaphragm moves up and down, hence

requiring the slack in the vessel. The splenic artery also

gives rise to the left gastro-omental artery which supplies

the greater curvature of the stomach. It also anastomoses

with the right gastro-omental artery to allow for this. The

splenic artery also gives rise to the short gastric arteries

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which supply the fundus of the stomach. The end of the splenic artery penetrates the hymen

of the spleen and feeds it with blood supply. Note that

it is important that the pancreas has a sufficient blood

supply as the secretion of insulin and the control of

blood glucose is dependent on it.

- Common Hepatic Artery: it gives rise to the right gastric

artery, the hepatic artery proper which leads to the liver

itself, and the gastro-duodenal artery which feeds the

duodenum. The hepatic artery along with the bile duct

and the carpel vein travel along the free edge of the

lesser omentum.

- Superior mesenteric Artery: supplies the small

intestines after the duodenum, the asceding colon and the first two thirds of the transverse

colon. The meso-appendix artery feeds the

appendix. You have duodenal arteries, iliac arteries,

jejunal artery, middle colic artery and the right colic

artery.

- Inferior mesenteric artery: comes out of the

abdominal aorta at around L3. It covers the last third

of the transverse colon, as well as the descending

colon, rectum and anus.

- Venous Drainage: the inferior mesenteric vein, is

supplied by all the structures that were fed by the

inferior mesenteric artery. The inferior mesenteric

vein however drains into the splenic vein and then

the hepatic portal vein, as all blood coming from the digestive

system with new nourishment must go through the liver first.

The superior mesenteric vein drains all the structures that

were fed by the superior mesenteric artery. They all come

together to form the portal vein. The portal vein sits in the

free margin of the lesser omentum.

- Lymphatics: there are three main lymph nodes that are the

celiac, inferior mesenteric, and superior mesenteric lymph

nodes similar to the vein they all line up. However they all

drain into the

cistern chyli

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Innervation (nerve input)

The entire gastrointestinal tract is supplied by the

autonomic section of the system. There are afferent neurons that

respond to chemical stimuli, mechanical deformation and radial

stretch. There are heaps of nerves that are intertwined into the

submucosa and the muscularis layer. When the body is in its fight

or flight mechanism the body prioritises away from the digestive

system. It is sympathetic nerves that feed the gastrointestinal

tract. So both enteric (sensory cells) pick up information and

autonomous (motor) neurons provide the changes.

Referred pain: is the fact that sometimes the sensory nerve that

feeds the internal viscera are connected to the brain with an external part of

the skin. This is why a person with appendicitis will present with pain around

the umbilicus region and not where the actual appendix is present. The brain

the appendix gets so swollen that it is moving other viscera triggering other

sensory input. In the same note this is why people with heart attacks

complain of pain under their left arm.

Draw up a flow chart that details the abdominal arteries

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Gastrointestinal Medicine and Nutrition week 3 summary

Histology of the Biliary Tree

Other than the main gastro intestinal tract that is

effectively one long hollow tube that breaks down

food, there are also many other organs that aid in

digestion known as biliary organs. These organs

include the Liver, pancreas, gall bladder, and spleen,

and they all play a role in aiding the digestive process.

The liver: is the largest organ in the body and it makes

a peritoneum which gives its appearance however does contain a bare area underneath the

coronary ligament is flush against the diaphragm. The liver is connected to the other parts of the

body by various ligaments. Firstly the falcciform ligament that runs

down the front of the liver separating it into left and right attaches

the liver to the anterior abdominal wall. An extension from the

inferior end of the falciform ligament is the ligamentum terres

which runs from the bottom of the falciform ligament to the

umbilicus. Secondly, there are left and right triangular ligaments

that attach the liver to the diaphragm. The liver is not only

separated into left and right sections with a Quadrate and Caudate

lobe being present as well. It is the inferior vena cava that burrows

into the liver that actually separates left and right.

As the liver has the function of cleansing the blood that comes from the gastrointestinal

tract it has two very different supplies of blood. One is the blood from the hepatic portal vein that

comes straight from the GI tract for cleansing, and the second is from the hepatic artery proper

which provides blood that is required for the liver to survive. The

term portal literally means that the vein is in between two beds of

capillaries, in this case the capillaries of the GI tract and the

capillaries of the liver. 70% of the blood that the liver receives is

from the hepatic portal vein, and only 30 % from the hepatic artery

proper. It receives about 1.5 L of blood per minute.

The arterial support comes from the common hepatic, then

the hepatic artery proper and then the left and right hepatic arteries

which go on to feed the left and right parts of the liver. From here

capillaries are formed obviously, and the veins system is very similar

just in reverse. The blood flows into the hepatic veins which then

lead to the inferior vena cava to head towards the heart. The

hepatic portal vein which supplies the liver with blood from the GI

tract has multiple branches that lead into it including the splenic vein, the superior rectal vein, the

superior and inferior mesenteric veins, and the superficial veins of the abdominal wall. The liver has

the 3 main roles in human function: store glycogen, clean blood and create bile. The vessels that

17 | P a g e

feed the body these three things all originate from the part of the liver called the porta hepatis

where the hepatic artery, the hepatic portal vein, and the

hepatic bile duct all leave the liver.

Histology of the Liver: At the most basic level the liver is

composed of lobules, that each have a hexagonal structure.

Each of the lobules contains a central vein with all the

hepatocytes leading in towards it. Where the three

hepatocytes meet you get a portal triad which contains three

vessels; a portal venuole, a bile duct, and a lymphatic arteriole.

At the portal triad you get these structures but it must be noted

that the vein is a lot larger than any of the other vessels due to

the purpose of the liver. The bile duct is made of simple

cuboidal epithelium. The bile in the liver is actually produced in

the hepatocytes however it dlowly drains to larger and larger

canals in the liver until it reaches the bile duct. It must be noted

that bile and blood flow are generally in opposing directions.

The Gall Bladder: is a sac that is found inferior to the liver, at it has the function storing the bile that

the liver produces and concentrating it so that it has a more potent effect on emulsifying the fat. The

gall bladder is divided into the body neck and fundus. The gall bladder is stimulated when a bolus of

food reaches the duodenum; this stimulates the release of cholecystokinin which further stimulates

the release of bile from the gall bladder. The bile enters the duodenum

and emulsifies the fat which makes it a lot easier to digest by the lipase

enzymes secreted from the pancreas.

Histology of the Gall Bladder: the gall bladder histologically consists of a

folded mucosa of simple columnar epithelial cells with underlying fibro

vascular lamina propria, and a deeper muscularis externa with a layer of

external elastic fibres and a serosa. There is no muscularis

mucosa or sub mucosa.

Gallstones can occur when excess cholesterol enters the gall

bladder and it forms crystals. The gall bladder must then be

removed from the patient. High amounts of pain can be created

by the gall stones, and the loss of it through the cholecystectomy

is usually well tolerated in humans.

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The Pancreas is a vital organ in the human body it is a secretory gland that has two vital roles. It

provides both endocrine and exocrine hormones. The endocrine function of the pancreas is the

insulin and glucagon that it produces that are supplied into the blood stream to help manage the

levels of the blood glucose. The exocrine function is

the plethora of digestive enzymes that it produces

to help breakdown the food that we eat. The

pancreas is divided into a head (surrounded by the

duodenum) a neck a body and a tail, and is also

said to be retroperitoneal. It sits slightly posterior

to the stomach and the

tail All the pancreatic

enzymes that are fed ito the duodenum are transported through small

vessels until it meets the main pancreatic

duct where it is led to the duodenum.

Histologically the pancreas is divided into

two distinct areas based on whether it is

supplying the endocrine or exocrine

function. The islets of langerham which only make up

approximately 1-2% of the pancreas by weight is where

the glucagon and insulin is produced. The other portion of

the pancreas produces the digestive enzymes. Many of

the enzymes that are produced in t

operate in the pancreas. These enzymes are only activated when they reach the basic pH of the

duodenum and this is a clever ploy by the body to stop self-digestion.

The Spleen is the final organ that is discussed it is a large soft vascular lymphoid organ. The spleen

has large immune qualities, and is an organ that is used for a lot of lymphatic

drainage. The spleen is fed by large quantities of blood and hence when it is

ruptured it does bleed profusely. If the spleen is ruptured in a child an

attempt will be made to repair it (due to its immune qualities), however if

the rupture occurs in an adult the spleen will simply be taken out in a

spleenectomy. The spleen is simply fed by the splenic artery and drained by

the splenic vein. An easy way to remember the spleen is that it is 1 inch

thick, 3 inches wide, 5 inches long, 7 ounces, and lies between the 9th and

11th ribs.

Synthesising Session Notes: Development of the GIT and the inguinal region

The very primitive Gut lining is shown right. You are able to identify the

three main blood vessels that supply the abdomen of the individual. The

cloaca is an embryonic derivative that disappears as the individual fetus

matures. By week 8 of the embryonic development all main organ

systems are in place, however in a very unrefined state. The liver of a

fetus is also very much larger than that of an adult.

Islet of

langerham

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During the development the trachea and the oesophagus are both one tube

that eventually becomes two through the trache-oesophagial folds coming in

on both sides and forming the two pipes (see image right). The respiratory

diverticulum, gives rise to the trachea and the bronchi which lead to the

lungs. Sometimes during development the two

m properly, leaving pathways

between the two. This can be life threatening

and requires immediate attention. By week 7 of

development the relative length of the

oesophagus is formed.

In the stomach development, initially the stomach is facing anteriorly

however it turns during development to form the lesser and greater

curvatures. The posterior portion of the stomach develops faster than

the anterior section, prior to turning. It rotates in a clockwise

direction 90 degrees. This is what explains why the Vegas

nerve serves the stomach. The duodenum develops in the

curved part because it runs out of space. The duodenum is

formed from both the foregut and the midgut, and hence the

proximal portion is fed by the celiac trunk and the distal

portion is fed by the superior mesenteric artery. The common

bile duct penetrates into the duodenum. The duodenum

becomes retro-peritoneal. During the early parts of

pregnancy the cells in the duodenum proliferate so rapidly

that the duodenum actually becomes slightly blocked.

However just prior to the birth it clears up.

The liver and the gall bladder both come about from a

small ventral outgrowth from the foregut, and they are

therefore fed by the celiac artery. The liver is relatively a

lot larger in a developing foetus than an adult. The liver

releases bile from week 12, and therefore must go through

enormous amounts of growth extremely early. At about

week 6 the liver makes up 10% of the weight of the baby.

The image right has the different levels of development,

weeks 5, 6, 7, 8. The pancreas also undergoes extremely

rapid development.

The midgut loop enters the umbilicus region during development because it runs out of space to

develop in the abdomen. It then turns to re-enter the abdominal

cavity. The small intestines go around forming the foiled structure.

The hindgut also develops simultaneously in their own fashion shown

right.

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The Inguinal region

In a male the testes must migrate from their position high in the abdomen to the extremities for

effective sperm production. While it migrates south it drags with it layers of the abdominal wall that

become part of the scrotum. However by protruding through the abdominal wall potential defects in

the wall form which can later end up in a hernia that requires surgery. The layers of muscle that are

moved through the migration of the testes are the transversalis fascia, the internal oblique muscle

and the external oblique muscle.

The inguinal canal is the pathway that the male spermatic cord takes, as well as the female round

ligament. There are two inguinal canals one on each side of the body. They are formed through a

deficiency in the transersus abdominus muscle.

The spermatic cord contain (look into HB notes) the ductus deferens the testicular artery, the

pampiniform plexus, cremaster artery and vein, nerves, lymphatics, and procesus vaginalis

remnants.

1. Direct Hernia is where the abdominal contents pushes down of the pariental peritoneum,

2. Indirect Hernia is where the abdominal contents gets pushed into the inguinal ring, and the

scrotum. In these cases you can get small intestines in the scrotum.

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Gastrointestinal Medicine and Nutrition week 4 summary

Gastrointestinal (GI) tract motility

As detailed in previous the Gastrointestinal Tract is a single long tube that extends from the oral

cavity all the way down to the anus. It has the primary function to supply nutrience to the body and

excrete waste products. The GI tract works at around an efficiency of around 90%. The primary role

of the nutrience that the body consumes is for looking after the basal metabolic rate, the second

priority is towards growth and finally fat accumulation.

The principle function of the gastrointestinal tract is achieved through motility and

secretion. These two aspects must be controlled carefully, to ensure that the body is able to take in

the full amount of nutrience from the body. Homeostasis must be maintained in the lumen of the GI

tract, and homeostasis for different parts of the GI tact is obviously different. Maintenance of the GI

tract integrity is also crucial due to the very unsavoury environments that are included in it. The

maintenance of the GI tract is hard. The GI structures are orchestrated by both neuronal and

hormonal signals.

The pH value of the mouth is between 6.4 and 7.3; the stomach has a pH of around 1.5 to

4.0, whereas the duodenum has a pH value between 7 and 8. And these pH values are crucial for the

maintenance of certain enzymes as they only work at certain pH.

The transit time for certain portions of the GI

tract is as follows. The oesophagus is between 5 and 10

seconds, the stomach 1-3 hours, the small intestines 7-9

hours and the large intestines 25-30 hours. These

numbers can change however; the fattier in the food

the longer that it is in the small intestines. The word

chime refers to the mixture of food and digestive

enzymes and mucous in the bolus of food. Other factors

can change these values, such as stress, illness, and

diet.

The sphincters in the body are as follows

- The upper oesophageal sphincter is between the pharynx and the proximal part of the

oesophagus.

- The lower oesophageal sphincter is between the oesophagus and the stomach

- The pyloric sphincter is from the stomach to the duodenum

- Iliocecal valve is the junction between the ileum and the cecum (or the small and large

intestines)

- On top of this there are two sphincters in the rectum: the internal anal sphincter and the

external anal sphincter. The internal anal sphincter is smooth muscle and the external one is

skeletal muscle (allowing for conscious control).

Pace maker zones:

1. In the stomach it is found in the fundus sets the peristalsis: 3 per minute

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2. In the duodenum: sets the rate of segmentation: 12 per minute

3. Transvers colon: one every 30 minutes

There are three temporary storage zones in the GI tract: the stomach, the proximal colon and the

rectum. There are no other temporary storage zones.

Motility in the GI tract, is necessary for many reasons. The muscle both relaxes and

contracts, to help with these factors. The following are resons for GI motility:

- Mixing the digested food

- Contact between digest and cells

- Propulsion of digesta

- Restriction or propultion in a region of the GI tract

- Restrict back flow

- Facilitate adaptive reflex

The stomach has a great ability to stretch with the about of food

that is within it. It can increase is size for a certain extent without

the pressure of the stomach going up, and then after that the

pressure goes up drastically. This is detailed in the graph right.

Tonic contraction is the continued parcel contraction of

the muscles, this can be found in the oesophagus, which is

continually toned and after the bolus of food goes through it

loses tone and then goes back to normal. It must be noted from

this that the GI tract elongates greatly after death due to the

lack of tone. The sphincters are also termed through a tonic

contraction. A difference between a toned and an untoned

sphincter can be seen.

Segmentation is the contraction of your circular

muscles in the muscularis externa layer. The main function of

segmentation is mixing the food as the food gets pushed together

more effectively. It is also involved in slow food propulsion. These

segmentation contractions are only known as segmentation in the

small intestines, in the large intestines it is known as haustral

contractions.

Pendula is the contraction of the longitudinal muscles and

peristalsis is the coordination of segmentation and pendula.

Peristalsis has three different names for the three

different regions: in the oesophagus and the stomach it is known

as peristalsis. In the small intestines it is referred to as the migrating motor complex. IN the large

intestines it is known as mass movement (MM). in the rectum it is the defecation reflex.

The reflexes that are found in the digestive system those are present to ensure that

feedback of the position of the digestive tract is under control. The reflexes are split into receptive

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and adaptive reflexes. There is a receptor in the mouth that detects increase in contents, which

sends a message through the Vagus nerve to the medulla oblongata for processing. Which then

sends out a motor response to the lower oesophageal sphincter to relax and open, a very little

accommodation reflex is also stimulated in the stomach. The neuro transmitter for these processes

is acetylcholine. Next stretch receptors in the lower oesophageal sphincter detect that again send a

message through the vagus nerve to the brain and back

to open the sphincter. Once it is past the stomach the

enteric nervous system takes over to control the digestive

system.

The stomach does not release all the contents

that it contains at once as the acidic properties if it will

have very big consequences in the duodenum. A very

little is allowed into the duodenum at each of the

contraction (3 per min). Small ejaculations from the

stomach are created to allow for appropriate

neutralisation time is necessary to maintain the integrity of the duodenum. Another factor that must

be considered is that the duodenum cannot hold that much food, that is so hypertonic that would

has entered the duodenum to neutralise the pH and get it to duodenal enzyme friendly levels.

Add in the images of the pacemaker zones. It must be noted that you sometimes get food

moving backwards due to segmentation.

Notes from the GLS

The functions of oesophageal motility is to ensure that the food is propelled in a downward direction

and stop upward flow more commonly known as reflux or heart burn. The digestive system must be

controlled carefully through the Vagus nerve to ensure that the sphincters open and close at the

right time. You can have a receptive response like the one to open a sphincter or an accommodation

response to allow the food to sit. Once food reaches the end of the oesophagus proprioceptors in

the smooth muscle layer detect pressure and send a message to the brain and back to open the

sphincter. A similar concept occurs in the stomach once food enters it and the proprioceptors detect

an increase in pressure messages are sent for the stomach to enlarge to accommodate more food.

The stomach has many features

including the action of peristalsis. Only small

quantities of food are ever injected from the

stomach to the duodenum, as the extreme

acidic environment of the stomach would be

harmful to the duodenum. The wave that is

created in the fundus migrates down the

stomach and ends in the pylorus. The Pyloric

valve in this motion plays a vital part as to not let through food, but to also ensure that the contents

of the stomach get thoroughly mixed. When a person vomits it is usually due to the contents of the

stomach creating too high a pressure, this stimulates the gastro-oesophageal sphincter to relax and

the soft palate to cover the nasal cavity. It is usually due to excessive pressure in the stomach,

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bacterial toxins, excessive alcohol or spicy foods. After vomiting since a lot of the stomach HCl is lost

the blood of the individual becomes alkaline in an attempt to compensate. It must be noted that it is

the three layers of the stomach that allow for it to create peristalsis in such an oddly shaped organ. If

gastric emptying is not well regulated it can create issues of self-digestion of the duodenum and

osmotic problems in the duodenum.

The control of the release of food into the small

intestines from the stomach has both hormonal and neural

input. The diagram right highlights these inputs in a well-

constructed out diagram. But basically what happens is: when

the presence of hypertonic chime in the duodenum is detected

two simultaneous pathways are stimulated. Firstly entero

endocrine cells secrete enterogastrones which decrease the rate

of emptying in the stomach. Simultaneously, chemoreceptors

and stretch receptors target via the enteric nervous system as

well as the CNS centres to decrease the contractile emptying.

Gastro Oesophageal Reflux: or GOR is a condition where gastric

contents flow up through the oesophagus through the lower oesophageal sphincter. GOR is usually

prevented by many factors including: gravity, Lower oesophageal

sphincter pressure, oblique course of the gastro-oesophageal

junction, and gastric emptying. The sphincter can become

unhealthy due to many factors including smoking and bad diets. If

the regulation of the sphincter and the gastric contraction does not

occur simultaneously there can be a reflux situation created. A

hiatus Hernia can also occur if the sphincter is not operating

appropriately.

GOR is something that is elevated when extra intra-

abdominal pressure created. Intra-abdominal pressure can be created by eating a larger meal, or

being pregnant, or by even undergoing strenuous resistance exercise. GOR is commonly referred to

heart and severe chest pain. The complications those are

associated with GOR if it is remains untreated for a long

period of time, is stricture and Barrett oesophagus. These

are both occurring when the cells tissue of the oesophagus

in the lower oesophagus sphincter die and the new tissue

that forms is scar tissue. This creates really painful GOR

from then onwards.

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Gastrointestinal Medicine and Nutrition week 5 summary

Gastrointestinal secretions and absorption

Functions of secretion are divided into three different categories, proteins ions and water. One of

the major functions of GI secretions is to maintain the homeostasis in the GI tract and ensure that

osmotic pressure is attained. Proteins functions include digestive enzymes, protection and

lubrication of the mucin and the immune-globulins. The ions are present to maintain osmotic

pressure. Acid and Base

properties are important for

different parts of the GI tract for

the function of the enzymes.

Water is the third type of

secretion that is required to help

with absorption of the different

substances.

Some secretory structures

that are present in the GI tract

include: Goblet cells, secretory

crypts such as the crypt of

glands, and finally organs such as the liver and the gall bladder. The goblet cell is obviously

unicellular and it secretes directly into the GIT. You get

multiple different types of duct complexes.

The basic structures of the cells that are

designed to do exportable proteins are extremely

asymmetrical. This is highlighted by the cell below. The

nutrience or anything that needs to be secreted can

come in through the capillary, come through the cell,

into the endoplasmic reticulum and the golgi apparatus,

and then finally the secretion.

The mucous layer in a cell is of vital importance;

it protects the GI tract from self-digestion. Some of the

environments that are found in the GI tract are capable of self-digestion. The mucous is divided into

two layers. The more inner, loosely adhered mucous, and the closer to the epithelium mucous layer

known as the firmly adhered mucous. The loosely adhered mucous can come off and mix with the

food if need be. However the firmly adhered mucous is a lot more important in the protection of the

stomach. It must be maintained to protect from acid burn. Other factors that are present to protect

the lumen include: cell type, compacted cells, quick cell turnover, alkaline mucous, and blood supply.

The destructive forces of the acid secretion mixed together with pepsin. The other harmful

-steroidal anti-inflammatory drug) these are aspirin or neurofen. What

factor that thins the mucous layer is the helicobacter pylori, which is the bacterium that forms peptic

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ulcers. It is able to spiral through the

mucous layer and is spread through

the sharing of fluids. The bacteria

works by the following manner shown

right. It does not actually eat through

the epithelium however it can eat

away the glue between epithelium

cells. It secretes ammonia which hide

it from the acid in the stomach. This

also has alkaline properties. Stress

and smoking cause extra acid

production as well.

To treat the bacterial infection what can be given are antibiotics to treat the infection.

Neutralising factors will decrease

the acidity of the stomach, and pain

relief for the patient. However a

careful pain reliever must be

chosen because many will have

negative effects in this situation.

Duct cells are found in the

pancreas and they secrete

bicarbonate juice that helps

maintain pH by acting as a buffer.

Membrane transport can be either active or passive. There are detailed notes on this

covered in MTC. Passive Transport includes; osmosis, and facilitated diffusion whereas active

transport is stuff such as the sodium potassium pump.

- Primary Active Transporter: is what creates a gradient and requires ATP

- Secondary transporter: then uses the gradient that has been set up by the primary

transporter for bodily functions.

- Symporter is a protein channel that carries two molecules from one side of the membrane

to the other side. It has the ability of using the energy of transporting one molecule down a

concentration gradient to bring another up the concentration gradient simultaneously. An

example of this is a glucose and sodium Symporter, that bring sodium downs its gradient

whilst at the same time bringing glucose up its gradient.

- Anti-porter in a protein transporter in the cell membrane that takes two or more items in

different directions. The sodium potassium ATPase pump is the primary example.

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The reasons that we as students are so interested in GI

secretions, is because there is so much of it. There are

enormous amounts of secretions and absorption in the GI

tract and it remains in balance.

Water also plays an important role in maintaining body

functions with roughly 60% of the body weight being

attributed to water. This is why it is so important that the

water gets reabsorbed in the large intestines.

The principle sites of water absorption are the

jejunum, ileum, proximal colon and gall bladder. The bile

that enters the gall bladder is concentrated up to 20 times

and this means that

The principle secretions in the gastric juices are

pepsinogen from the chief cells, acid from the parietal cells,

and intrinsic factor also from the parietal cells. Mucin is also

secreted from the goblet cells to help protect the stomach

from self-digestion. The stomach is protected against acid

by the mucosal barrier and the effect of prostaglandins

which stimulate the secretion of mucin.

GLS-Gastric acid secretion

There are three agonists for acid secretion in the body. Each one plays a different role in the process

and can be manipulated at different levels to get the desired result for the person. Gastrin which is

an endocrine agent acts on the gastrin receptors found on the basement membrane of the cells. It

has the effect of stimulating the release of the hormone Histamine which is a paracrine hormone

that acts on the local area cells. Histamine attaches to the H2 receptor which stimulates a chain of

events inside the cell using cAMP pathway to secrete HCl into the stomach. The third mechanism

that can be used to increase stomach acidity levels is through the nervous system using the

neurotransmitter acetylcholine pathway. Acetylcholine is released from the Vagus nerve and it acts

on the acetylcholine receptors to utilise the CAM pathway to release HCl into the stomach.

There are also a variety of drugs that can be taken to reduce acid secretion. These are useful to be

taken when a person has a stomach ulcer or is secreting to much HCl naturally. Ranitidine is a drug

that blocks the histamine from binding to its H2 receptor. This will stop the pathway through the

cAMP that is used through the histamine. Acid secreation will not come to a halt however when this

drug is being used, as the acetylcholine pathways is not affected at all. If you want to stop both

pathways the drug omeprazole must be used as it has the ability to block HCl from being secreted.

Substances that enhance acid secretion include pentagastrin that is simply a synthetic form of

gastrin that works in the exact same manner. Caffeine also has the effect of increasing acid secretion

as the it inhibits the phosphodiester enzyme in the cAMP pathway which creates twice the amount

of acid from the gastrin / histamine system that would be usually created.

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Blood that is leaving the stomach during the stimulation of acid secretion would be slightly basic as

the acidic ions will be stolen from the blood stream to be put into the stomach.

GLS - Control of secretion in the salivary glands, pancreas, gall bladder and intestines

The sublingual glands are found in the mouth and are one of the salivary glands. It secretes mostly

mucous into the mouth. The parotid glands are also a salivary gland in the mouth and it secretes

amylose and amylopectin.

There are three types of cells that are found in the gastric glands.

- Chief cells: secrete pepsinogen and lipases

- Parietal cells secrete hydrochloric acid

- Entero-endocrine cells secrete histamine, serotonin and gastrin

the duodenum is what secretes an alkaline solution in the

duodenum to help neutralise the stomach acid that is entering. In the small intestines you will also

find the crypts of lieberkuhn that secrete intestinal juices to help the chime travel down the

intestinal tract. The crypts of lieberkuhn contain cells deep in the crypts that have the role of

microbial defence. If a bacterium is able to get through the acidic stomach and the basic intestines it

will be attacked by lysozymes and antibacterial enzymes from here.

The gall bladder serves the function to concentrate and store bile. Bile which is a yellow alkaline

solution contains salts, pigments, cholesterol, triglycerides, phospholipids and electrolytes. The bile

plays the role to help emulsify the fats that come through to the duodenum. After the injestion of a

big fatty meal the bile salts return, secretin is then releases which the bile into the duodenum. When

there is little food in the duodenum the bile salts are able to be reabsorbed by the ilium and then

used again. This phenomenon is known as entero-hepatic circulation and is a mechanism that is

useful to conserve energy. In the absence of bile the faeces of the individual will be grey-white in

colour and would have fat streaks through it.

When bile stones accumulate and block the duct, stopping bile from being secreted into the gut, bile

salts are secreted into the blood and deposited on the skin. This deposition creates a disease known

as jaundice where the skin appears yellow. It must be noted that jaundice can also be attributed to

liver problems.

The pancreas is another crucial organ in the digestive system. It secretes pancreatic juice that

contains many vital enzymes in digestion and the maintenance of an effective pH for the duodenum.

Pancreatic juice release is controlled by the enzymes secretin and cholecystokinin. Secrete which is

released due to high amounts of HCl in the duodenum causes the pancreatic ducts to secrete

bicarbonate solution. Cholecystokinin is released in response to excess proteins and fats in the

chime and stimulates the release of pancreatic juice. The entero-endocrine cells that are found in

the duodenum secrete both cholecystokinin and secretin.

Synthesising Session discussion questions (a week overview)

The stomach and duodenum have many to stop it from self-digestion:

the rapid proliferating and tightly packed together epithelium, the mucous layers that protect it he

29 | P a g e

Brunner s gland secreting alkaline solution. Of the three the mucous lining will probably be most

important.

As in the case study if a person has helicobacter pylori and stomach ulcers the treatment plan

bicarbonate to neutralise the stomach and take antibiotics to treat the bacterial infection. Some

factors that increase the chance of stomach ulcers other than the bacterial infection are the

decrease

the amount of stress in the lifestyle. Increased stress levels in a lifestyle create glucorticosteroids

that increases the acid production and in turn can lead to the dereas e of the mucous lining and

therefore stomach ulcers.

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Gastrointestinal Medicine and Nutrition week 6 summary

Digestion and Absorption (CHO / Proteins)

For a person to survive they must get adequate food from all three sources. Carbohydrates, Proteins

and Fats must all be broken down in the GI tract prior to them being absorbed and then used for

their necessary purposes. It is recommended for people to have a diet that pertains of 45-65%

carbohydrates, 15-25% protein and 20-35% fats.

Carbohydrates are sugar units that come in various different sizes. The term saccharide is the basic

sugar unit, with monosaccharide being a single unit, disaccharide being a double unit,

oligosaccharide being a unit between 2-10 molecules long and a polysaccharide being longer than 10

units. Polysaccharides can further be divided into two groups starch polysaccharides and Non starch

polysaccharides. The non-starch polysaccharides are crucial in wheat and fruit and help with

digestion as they are not digested in the small intestines. There are three monosaccharides: glucose,

fructose and galactose. There are also three disaccharides; maltose,

lactose and sucrose. The major form of glucose that the body receives is

starch. Starch is easy for the body to breakdown as it contains many ends

that are able to be oxidised. The glycaemic index is very closely

associated with this factor of the amount of oxidisable ends. Once the

carbohydrates are broken down they are then stored in the muscle tissue

and the liver, with excess being stored as fats.

When carbohydrates are being digested; there are numerous places that facilitate the

breakdown. The digestion of carbohydrates begins in the mouth; the salivary amylase that is

secreted from the serous cells helps to break down the starch. The pH of the mouth is between 6.3

and 7.3, to enable the salivary amylase to work effectively. There is surprisingly no breakdown of

carbohydrates in the stomach. When the chyme enters the small intestine, the release of pancreatic

enzymes such as alpha amylase acts to breakdown the starch into oligosaccharides and

disaccharides. The trigger for the release of the pancreatic enzymes is in the duodenum.

message travels to endocrine hormones to act on the pancreas that produces the enzymes.

The brush border is the next phase of digestion: the brush border is attached to the mucosa,

they are membrane bound, and this is

why segmentation to produce a

thorough mixing, to allow for the

most amount of absorption. At the

brush border is where the

disaccharides are broken down. The

brush border is highlighted by the

following diagram. In the end you get

the three monosaccharides from the

large starch molecules. You get multi-

functional brush border enzymes that

contain two active sites.

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Non-starch polysaccharides, as shown in the diagram, do not get digested in the small intestines but

must be digested by micro-organisms in the large intestines. There are bacteria that are found in the

large intestines that help with this

acetate, propionate, and butyrate are formed to be used in the body. There is a lot of gas that is

created in the large intestines every day (some comes out as

flatulents but the majority is absorbed and breathed out).

Carbohydrate Absorption: occurs in both the small and the large

intestines. In the jejunum there are Symporter that are being used

to bring an ion and a glucose molecule at the same time. Glucose

is absorbed straight into the bloodstream, and the levels of

glucose in the blood are controlled by the amounts of insulin and

glucagon that are created. People that are unable to control the

amount of glucose that they have in their blood are termed diabetics. These people either lack the

ability to produce insulin or have lost the ability, hence are susceptible to hyperglycaemia. Diebetics

faint due to either abnormally high or abnormally low glucose levels. Blood glucose levels between

4mM and 8mM are normal levels.

Obviously not all carbohydrates are absorbed by the body at the same rate. The rate at which

carbohydrates are absorbed into the blood is compared on a scale known as the glycaemic index.

Foods that are absorbed quickly have a high glycaemic index and vice versa.

Guided Learning Session

Protein breakdown occurs in 3

main steps; shown right. The pH

sensitive pepsin breaks down

the large proteins into large

polypeptides. Pepsin has the

ability to cleave bonds that are

attached to phenylalanine and

tyrosine, but none of the other

bonds. Pepsin hydrolyses about

15% of the protein.

The pancreatic enzymes

which further break down the

protein are trypsin and

chymotrypsin; cleave the polypeptides to even smaller molecules for the brush border enzymes to

further degrade. The brush border enzymes include: aminopeptidse and dipeptidase facilitate the

final break down of the proteins to the individual amino acid level. Brush border enzymes are

attached to the membranes of the plicae circularis in the small intestines, as they are not free

moving proper gastrointestinal tract motility is important to allow for adequate segmentation and

thus thorough absorption. Since proteins are everywhere in the body as a part of the cell structures

it is vital that they are produced in an inactive state and become active in the GIT. All stomach and

pancreatic enzymes possess this ability and it is crucial to stop auto-digestion.

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The recommended daily intake for protein is 125 g per day. In this serving it is important

that the individual gets the essential amino acids as the non-essential amino acids can be

manufactured in the body. Animal products are the major source of protein in a human diet and

hence those that are vegetarians must carefully watch their diets to ensure that they get the

adequate foods.

The absorption of protein is through several types of carriers that transport specific amino

acids across the small intestines order. Small chain dipeptides and tripeptides are able to be co-

transported into the epithelium cells with H+ ions. In certain situations small proteins can be

absorbed intact through endocytosis; however this is rare as the entire could be seen as non-self and

hence an immune action may be triggered in the blood. In newborn babies however it is common for

complete adsorption of proteins across the epithelium. This is a mechanism to get the IgA antibodies

ve they some passive

immune ability. As young babies have this ability it is extremely important to keep them sheltered

during the first few days of life as this is when they are susceptible to build up allergic reactions to

proteins that do cross the epithelium and are recognised as non-self.

Synthesising Session: Maintaining GI balance and integrity

Coeliac disease: is where a person is unable to absorb gluten properly. If the person eats too much

gluten the protein (gluten) causes damage to the villi of the small intestines which become inflamed

and atrophy. Digestion and absorption are affected a fair bit by this disease if the person continues

to consume the gluten as the small intestines will not be able to absorb the other foods as

effectively due to the damaged microvilli. People that are coeliac can avoid gluten in their diet and

live a normal life.

Pancreatitis: is a disease for the inflammation of the pancreas, it is caused when the digestive

enzymes which the pancreas secretes get activated in the pancreas itself instead of the GIT. This

causes auto-digestion of the pancreas. Pancreatitis can be caused through severe alcohol

consumption, and other infectious disease. High blood calcium concentration is an indication that

pancreatitis is present, so is raised serum amylase concentration.

Lactose intolerance: is a condition where a person lacks the lactase enzyme in their brush border.

This causes lactose to be not absorbed effectively, and hence it slips through the digestive tract and

causes diarrhoea. People with

lactose intolerance have to avoid

milky products.

Shown right is the varying types of

stool that are created by people;

normal stool in in between 3 and 4.

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Week 6 Integrative

Treatment of peptic ulcer disease

- Antibiotics are administered to treat the helicobacter pylori infection

- Acid channel inhibitors are also administered to stop the secretion of stomach acid into the

stomach

- Over the counter medication that contains salts as well can make the environment more

basic and less harmful for the patient

- The consumption of smaller more regular meals is advised as well as meals that contain less

fat.

Terminology:

Diarrhoea: an increase in the frequency and fluidity of bowel

movements due to mal-absorption of water. This is tied in with loss of

fluids over time and is usually the first sign of a GI tract disorder.

Constipation: is small, difficult and infrequent bowel movement (less

than 3 stools per week)

Zymogen (pro-enzyme): is an inactive enzyme precursor (such as

pepsinogen is to pepsin)

You can test the efficiency of somebody with poor bile secretion

through the amount of fat that is coming through their stool. Increased fat entering the intestines is

linked to increased chance of colon cancer since their would be greater amounts of abrasion in the

intestines leading to greater amounts of proliferation, and a greater chance of a cancer mutation

occurring.

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Gastrointestinal Medicine and Nutrition week 7 summary

Liver digestion and Absorption; Liver function

The liver is the largest internal organ in the human body; it weighs on average 1.4 kg in an adult and

has the crucial role of creating bile for fat emulsification, CHO, lipid and AA metabolism, waste

removal, vitamin and mineral storage, and dismantling of RBC.

Bile which is formed in the gall bladder gets stored and concentrated in the gall bladder. The gall

bladder is a non-essential organ as people that have gall stones quite regularly have it removed in a

cholecystectomy. Bile Acids and Salts are derivatives of cholesterol synthesised in the hepatocytes.

Cholesterol is converted into bile salts however when excess cholesterol is present the gall stones

can be formed due to their crystallisation in the wrong place. Bile is secreted in the hepatocytes of

the liver and makes its way through the canaliculi into larger and larger bile channels and to the gall

bladder for storage. When there is fat in the duodenum there is a

chemoreceptor (CCK in the I cells and Secretin in the S cells) that

picks it up this situation and stimulates the gall bladder to

contract, and to relax the sphincter of Oddi, causing bile to be

secreted into the duodenum.

The lobules of the liver contain three 3 features: the hepatocytes

that are parenchymal cells that are arranged in platelets. The

sinusoids are the channels that lead to the portal triad, and lastly

the portal triad is at the corner of each lobule, and it contains a

bile duct, a portal venuole, and a portal arteriole.

The sinusoids are small vessels that can allow the substances that

are formed in the liver to be extracted out to have their effect in the body. The sinusoids are lined by

endothelial cells so that substances are able to flow through the epithelium however the mass blood

vessels are not able to. There are large quantities of blood that traverse through the liver, 75%

comes from the hepatic portal vein which is being fed from the capillary arteries and 25% comes

from the arteries more directly. These different blood sources have varying purposes for entry into

the liver. The arterial fed blood has the purpose to maintain the integrity of the liver, and ensure

that it is nourished with adequate ions

and oxygen. The blood that is fed from

the portal vein is in the liver to be

cleaned and detoxified prior to leaving

between the endothelial cells and the

sinusoidal cells there is space for disease, although there is lymphatic drainage present infection can

still set in.

The composition of bile is important to the function that it undertakes, it must be contain bile salts

that are amphipathic in nature, water, electrolytes, cholesterol, phospholipids, bilirubin, and other

t important aspects that will be phospholipids

and cholesterol.

35 | P a g e

When cholesterol is discussed as of metabolism and creation it is considered as a fat. Cholesterol is

normally created in the liver, and hence people that have cholesterol problems are usually

predisposed to it. However when people have cholesterol issues, a low cholesterol diet is still

advised along with the drugs that have an affect lowering the blood cholesterol.

The gall bladder will concentrate the bile up to 5 times by taking away water from there as

the solution. The bile is modified as they flow through the ducts of the gall bladder in a similar

mechanism to the pancreatic juice. There is an addition of watery bicarbonate secretions as the bile

continues. Adult humans produce on average 500

mL of bile each day.

Enterohepatic circulation is the

reabsorption of the bile through the ileum. Bile can

be recycled 18-20 times this is to ensure that high

blood stream. This is a clever mechanism the body

utilises to decrease the amount of waste bile that is

being excreted in the faeces.

Bile has a vital function in two different roles:

- Bile salts are required for critical digestion and absorption

- Waste products are often removed from the body using bile. They eventually head out through

the faeces. Drugs, Alcohol and a lot of other substances are removed from the body in with the

use of bile. Some compounds that are reabsorbed in the small intestines ultimately eliminated

by the kidney through urine. Bile is also the main way for the body to eradicate excess levels of

cholesterol, as excess levels of galls stones lead to gallstones through the crystallisation of the

gall stones.

Digestion and Absorption of Lipids:

Lipids are a crucial par

supply of dietary fat means that the individual may be at risk of

absorbing the necessary minerals to survive which could be fatal.

or triacylglycerol they usually house the vitamins A, D, E, and K. The

other 5% of the fats that are consumed by the body are the

(triacylglycerols). As fats are insoluble in water they will always stay

together in the watery environment of the small intestines. This is

where bile comes in to play the role to split the fat into millions of

small pieces. The individual units that are covered by the bile salts

are known as micells. This increases the surface area to volume ratio and makes it easier for the

pancreatic enzymes to break down the smaller fat molecules into their respective fatty acids and

glycerols. If the enzymes were eating around one big fat globule then the fat digestion would be a lot

slower. There is a very small amount of stomach, gastric lipase, in the stomach however it is very

minor. The chime is homogenised and released into the duodenum, then the bile is secreted that

36 | P a g e

emulsifies the fat which then allows the pancreatic enzymes to work efficiently. The break down

products is fatty acids and 2 monoacylglycerol. At this stage the molecules are still in a micell stage.

After this when the fatty acids and the 2 monoacylglycerol are actually absorbed by the absorptive

cells or the enterocytes of the small intestines. Once in the enterocytes the endoplasmic reticulum

then simply put the triacylglycerol back together the Golgi body in the cell then adds a protein to be

packaged as chylomicrons. A chylomicron is basically a triacylglycerol with a skin of proteins around

it to get it into the basal membrane of the cell to go into the lymph tissue as the capillaries are too

large. The chylomicrons then enter the blood stream through the left

sub-clavian vein, where it will head to the liver to be processed. The

steps are: emulsification, breakdown, absorption, putting together,

chylomicron, and into the lymph vessel. The process seems very

counter-productive as the triglycerides are simply molecules simply

get smaller and then bigger again, however, the reason for this is to

ensure that they are able to cross membranes with ease.

The crucial differences between lipid breakdown and the

breakdown of CHO and proteins is that there is no brush border enzyme

breakdown of lipids as the lipids would simply be able to slip straight

through the membrane. The enzymes that breakdown lipids are never

membrane bound.

The large molecules of fats are the only ones that get through the

chylomicrons, the smaller fatty acids are able to get into the bloodstream,

and go to the liver. In the liver, you get the triacylglycerols that broken

down into glycerols and fatty acids again. These go into the bloodstream and are transported to the

adipose or the muscle cells where they are required. The remnants of the chylomicrons get broken

down and reused in the liver, they are packaged to produce VLDL (very low density lipoproteins)

which are a lot of triacylglycerols, phospholipids and cholesterol packaged together.

A high density lipid is pretty much a protein shell that does not have any fat; they have the

purpose of going into the bloodstream and collecting cholesterol. The low density lipids are said to

be the bad cholesterol as they can clog the arteries. HDL is good, LDL is bad. There are drugs that can

be placed to stop the digestion of the fats being digested and absorbed. This will lead to greater

amounts being excreted in faeces.

Olestra is a synthetic lipid that makes

food fatty like, however it does not get

digested. This allows people to have

the tasty fatty foods that fill the

stomach for longer; however, the food

goes straight through the system.

The final thing that needs to be

considered is the breakdown of Red

blood cells. It basically happens as per

the following diagram.

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Notes from GLS:

- Bilirubin must be carried on a albumin molecule in the blood stream as it is not very water

soluble.

- The enzyme in the liver that processes bilirubin is UDP-glucobonate transcarboxylase, it

produces conjugated bilirubin

- The iron in the red blood cell is stored as ferritin and is released back into the blood stream as

required with new RBC

- Jaundice is the yellowing of the skin and is formed by excess levels of bilirubin being found in

the blood. Bilirubin is yellow in appearance and that is why the skin turns that colour.

When there is a hepato-cellular inflammation of the liver, there signs in a blood test for damage are

increased levels of blood albumin, increased levels of bilirubin, and increased levels of lactate

dehydrogenase.

Synthesising Session Biliary Disorders

The term biliary means of or relating to the bile duct, hence a biliary disorder is one where the bile

duct is impeded or damaged is some manner. The major cause of blockage is gall stones which are

cholesterol crystallisations. Other forms of biliary disorders are cancers, autoimmune, and

congenital diseases. Different people are obviously at different risks of getting gall stones, however

the 5 key features that have been attributed to gall stones are: fat, fair, fertile, female and forty.

Obesity and rapid weight loss have been associated with the onset of gall stones, so have increasing

age, pregnancy, and some drugs. It must be noted that in most people gall stones are asymptomatic,

and hence show no signs of pain, only when the stones impede into the pathway of the bile duct do

people require a cholecystectomy.

Gall stones are constantly kept in check by the bile acids, lecithan and the cholesterol.

However when there is super-saturation of cholesterol either by genetic or dietary input the stones

can become too large and out of control. Gall Stones can be divided into separate categories,

cholesterol gall stones contain greater than 80% cholesterol, bile pigment

stones contain less than 20% cholesterol, and mixed stones contain between

20 and 80% cholesterol.

Acute Cholecystitis is infection or inflammation of the gall bladder.

The patient would present with abdominal pain (most commonly right upper

quadrant) that may radiate to the right shoulder or back. The pain is steady

and severe, with associated complaints including nausea, vomiting and

this test you ask the patient to inspire as must as they can and they using

your hands to palpate under the rib cage. People with gall bladder

inflammation would usually have heightened levels of pain or suffering

through this movement. By telling the person to breath in you are exposing the gall bladder the most

since the liver will rise with the diaphragm. When the patient presents they

will usually be voluntarily and involuntarily be guarding the area with their

limbs, they may also often have tachycardia. Once the person is tested

38 | P a g e

thicker gall bladder wall. Fluids and pain relief are administered to comfort the patient as much as

possible antibiotics are administered to treat the potential bacterial infection and once they have

been settled a cholecystectomy is undertaken.

Bile Duct stones (choledocholithiasis) is a slightly different situation where the patient would present

of manners; firstly ERCP can be used to get a thorough understanding of the situation, and then a

cholecystectomy could be used. A

cholecystectomy is simply an intra

operative cholangiogram that leads to

stone removal. ERCP is shown in the

diagram right, the main function of ERCP

is to inject a die that colours the gall

stones so that you can get a very clear X-

ray showing what is in the abdomen. A

small incision must be made to pierce the gall bladder duodenal sphincter, the sphincter of Oddi.

If there are gall stones that are present but they do not obstruct the biliary the patient will still be in

pain however, there will be no liver obstruction thus no inflammation of the liver and in turn normal

blood tests. People that have biliary problems would get greater amounts of pain 3 or 4 hours after

eating heavily fatty meals because the duodenum would be calling for more bile creating the pain.

39 | P a g e

Gastrointestinal Medicine and Nutrition week 8 summary

Metabolism in the liver

The liver has many crucial roles in the human body. It plays as essential role in the management of

glucose concentrations, and maintains homeostasis in the body through periods of starvation and

excess food availability. The liver also has a crucial role in the management of drugs that people take

and when the liver suffers the entire body suffers the consequences. The liver has a very varied role

and that is why people require liver transplants when their liver fails. The liver serves so many

functional purposes with:

- Carbohydrates: as it both stores and secretes glucose into the blood stream as required,

through the processes of glycolysis and gluconeogenesis

- Proteins: synthesis and catabolism, along with amino acid metabolism and urea synthesis

- Lipids: it is involved in lipoprotein and cholesterol synthesis along with fatty acid metabolism

and bile acid synthesis

- Excretion and detoxification: bile acid and bilirubin excretion, drug detoxification, steroid

hormone inactivation and excretion, alcohol metabolism (more than one unit every hour)

- It is also involved in iron storage and Vitamin A, D, E and B12 storage and metabolism.

- Drugs: any type of drug (over the counter, prescription

and illicit) that you put into your system are put

controlled and detoxified by your liver.

The liver is the major controller of food substrates in famine

and in feast conditions. The amounts of glycogen,

triacylglycerols and proteins are all controlled by the liver, and

then are either synthesised or degraded during times of feast

or famine respectively. The liver is able to create glucose

through gluconeogenesis, from pyruvic acid. This pathway can go either way, in famine it will secrete

glucose into the blood to keep you alive, however in times of feast it does not require the glucose in

the blood stream and the glucose 6 phosphates is converted into glycogen.

Drugs: the majority of drugs that are taken are lipophilic so that they can cross the cell

membrane and be active where we want them to be. Because of their lipophilic trait they are unable

to be processed by the kidneys and end up being processed by the liver in a two phase manner. The

first stage is where they go through a

catabolic stage where a hydroxyl or a

methyl group are added in order to

detoxify the drug, this usually occurs

in the smooth intestines catalised by

cytochrome P450 mono-oxygenases.

Stage II occurs in the hepatocytes to

produce an inactive soluble product.

The basic processes of drug

metabolism are detoxification and

then make it soluble to be excreted

by the kidneys. Non polar drugs will

40 | P a g e

simply accumulate in one part of the body. This is why drugs must be taken in the correct

moderation, so that the pathway does not get overloaded, as the particles will build up too much

and the free radicals that are created are not able to be excreted in time creating issues.

Carbohydrate Metabolism: in times of feast we store the glucose, and in times of famine we

obviously use it for energy. 60% of the carbohydrates that we eat are absorbed by the liver to be

placed in to storage pathways. The remainder goes into the blood

stream, which allows glucokinase to phosphorylate glucose,

increased glycogen synthase, increased glycolysis and decreased

gluconeogenesis. When glucose gets absorbed it is almost always

converted to glucose 6 phosphates, and then there are four

pathways that can go from here, detailed right.

Protein Metabolism: the liver is responsible for making a lot of the

proteins in the body, things like albumin and coagulation factor are made in the liver. The amino

acids can be converted to TCA cycle intermediates; however can only be stored in the muscles. The

muscles are sometimes broken down to create energy but

this is only in times of absolute starvation. As amino acids

can only be stored as proteins increased level of protein

uptake is useless unless you are getting muscle damage to

help to get bigger otherwise you are just creating expensive

urine. The proteins that are secreted by the liver include the

ones shown in the table right. There is a difference between

glycogenic and ketogenic amino acids that break down into

glucose intermediates or ketone bodies. These are both able

to be used for energy supply.

Fat metabolism. The liver is responsible for synthesis of

triacylglycerols, synthesis lipoproteins, and synthesis of

cholesterol. Cholesterol is used in the body to help the

fluidity of the cell membrane and a precursor to both

steroid hormones and bile salts. One of the important aspects about fatty acids is that it cannot be

converted into glucose; it must become a ketone body. The liver synthesises ketone bodies to be

used by the body for energy. In human the majority of energy is generated from lipid breakdown.

Lipids are stored as triacylglycerols in the adipose tissue and then they are broken down by lipases to

be used to create energy. They used in

the mitochondrion to create energy. It

is important that lipid levels stay

normal, otherwise the body could use

muscle and to create energy.

Summary of Liver Metabolism: there

are basically three levels that the body

can be functioning under, high energy

substrate levels (straight after meals),

low energy substrate levels (between

41 | P a g e

meals) and starvation. A detailed representation of what occurs at the different tissues is shown

right.

Lipid Transport is an important function in the body. They are required for the

synthesis of the cell membrane, which is crucial for the structural integrity of

the cell. Lipids are transported through the blood stream on lipoproteins, as

they are insoluble in water. A lipoprotein is a spherical particle with

hydrophobic molecules such as neutral fat surrounded by phospholipids free

cholesterol and Apo proteins.

Density of lipoproteins: Chylomicrons are created in the small intestines are

extremely low density; they travel to the liver and other tissues. In the liver

t the body. The Apo proteins that are

found on the coatings of all the lipoproteins are extremely specific to get the

lipid to the area where they are needed and not just randomly floating in the blood stream.

VLDL (very low density lipoprotein) export triglycerides to the peripheral tissue. The peripheral

tissue then strips the lipid from the lipoprotein, and forming an IDL (intermediate density

lipoprotein). It must be remembered that as lipids are light

the, the lower the density the higher the lipid content. They

are synthesised in the liver and are usually 90% lipid. As

created from this and are secreted into the blood stream.

HDL (high density lipoproteins) are also synthesised in the

liver and they contain very little or hardly any triglycerides within them. They have the primary role

of going out and collecting lipids from the peripheral tissue and bringing it back to the liver. This

process is known as reverse cholesterol transport. They are usually 48% of protein and are hence

high density. The cholesterol is absorbed through receptor

mediated endocytosis. The process of how they absorb

cholesterol is shown right.

Chylomicrons are the lowest density (98% lipid) and largest

lipoprotein, they contain mediators on the outside of the

cell that serve the purpose get them broken down in the

-48, which is a

receptor bonding, Apo C-II which is a lipoprotein lipase

activator, and Apo E, which is a remnant receptor binder.

Chylomicrons are synthesised in the small intestines and

transport dietary lipids. Each lipoprotein has specific targets

the blood stream. They are produced in the epithelium cells of the small intestines but are too big

for the capillaries in the small intestines and therefore must be transported through the lymphatic

system. Once the chylomicron has released the fats that it is transporting the liver eradicates the

remnants of the protein coat.

42 | P a g e

IDL

precursor to low density lipoproteins. They have the same Apo proteins as the VLDL

LDL

here is a Apo B-100, the Apo

proteins keep getting taken off as

the process goes on. The LDL is the

bad cholesterol, because it has a

high level of cholesterol in it, we do

not want too much of it floating

around our boy. HDL are also known

as good cholesterol because they

contain a very low amount of

cholesterol, and they have the role

of going out and collecting

cholesterol and bringing it back into

liver. The receptors that help to

bring the cholesterol in are receptor

mediated, and hence when the cell is full of cholesterol they cut off the receptors and then no other

cholesterol is taken up.

In a healthy cell the level of cholesterol formation and degradation is at a relatively equal level,

however people can have genetic faults or develop problems through life where they lost this

balance causing excess levels of cholesterol to be released into the blood stream. This can cause

major problems. One of these problems are atherosclerosis; where they are unable to uptake the

cholesterol as the receptor is defective. This means that greater amount of cholesterol accumulate

of the outside of the cell, that cannot be digested. This then creates larger and larger lipid balls. This

is shown in the diagram right, with normal on top and

atherosclerosis on the bottom.

Overview of the lecture was the general function of the liver in

the control of homeostasis and the manner in which lipids are

controlled in the blood stream.

Guided Learning Session Notes

- Cholesterol is able to become hydrophilic if it becomes

a cholesterol ester as there will be an OH group on the cholesterol.

- Triacylglycerols are always converted back into glycerol and three fatty acids before they can

be up taken by the cells.

- The liver is described as the major source of both triacylglycerols and cholesterol as although

it does not actively store either of the molecules it is involved in the packaging of lipids into

triacylglycerols and the creation and organisation of cholesterol.

- Excessive Alcohol consumption causes loss of homeostasis leading to insulin resistance of

the cells and inflammation of the liver leading to steatosis. The lipase enzyme is activated by

insulin hence when the cell becomes insulin resistant the lipase can no longer be activated

43 | P a g e

leading to an accumulation of fat in the cell. Cirrhosis (replacement of the liver tissue by

fibres scar tissue) which leads to loss of funciton is often the outcome of chronic alcohol

consumption.

- Free Fatty Acids are transported through the blood on the protein serum albumin.

- The five different lipoproteins in order of size are: chylomicrons, VLDL, LDL, IDL, HDL. When

considering density the order is simply reversed.

Cholesterol is synthesised from the starting material acetyl-CoA, along with all lipids. Two acetyl-

-hydroxy-3-methyl-glutaryl, this reaction is catalysed by the enzyme,

HMG-CoA reductase. This enzyme is controlled in three manners to ensure that too much

three mechanisms are:

- Cholesterol feedback actually inhibits the HMG-CoA reductase gene from being activated

- Cholesterol also is a destructive force against the enzyme

- It is inactivated from phosphorylation. It is of importance to the health community to inhibit this enzyme because then you could treat people that are having high cholesterol levels.

Synthesising Session: Inflammatory Liver Disease

When the liver becomes inflamed due to a variety of reasons the end result is scarring

through collagen fibrosis. A patient that is presenting with liver problems a history is vital since the

lifestyle that somebody lives has a big impact on the health of their liver. Signs of chronic liver

problems include jaundice which can be

first identified in the eyes. Blood Tests

are looking for raised levels of hepatitis

antibodies, as well as liver enzymes in

the blood stream, as that could indicate a

leak. Inflammation of the liver can be

caused by a plethora of reasons that are

highlighted in the figure right. The main

causes are: infection, autoimmune,

metabolic, heredity, and drug or toxin

induced causes.

If when seen under a CT scan the liver is

bumpy the person probably has sclerosis

or scarring of the liver. Hepatitis B could

be the cause however it must be quickly

identified if the person is chronic or acute. If antibody E is found in the blood then it means the

person has chronic problem (particular antibody takes 6 months to appear).

Hereditary Problems with the liver may be related to iron levels, or copper amounts in the

body. Both of this elements need to be maintained carefully.

44 | P a g e

As the liver is the site for a lot of the drug mobilisation, it can be affected by drugs easily.

This includes over the counter medication, herbal remedies and illict drugs. Anti-biotics is the

number one cause of the drug related liver failure.

Interesting Side note:

- Any activity that increase abrasion on a surface increases the chance of cancer. This includes

sun burn, abrasive foods in the gastrointestinal tract, or smoking. The increased amount of

abrasion or cell damage means that increased levels of proliferation are required leading to

a greater chance of a spontaneous mutation occurring that causes cancer.

- Metabolic syndrome: is a combination of medical disorders that when occur together

increase the risk of heart problems and diabetes. The requirements for someone to have

metabolic syndrome are the presence of one of: diabetes, impaired glucose tolerance,

impaired fasting glucose, insulin resistance as well as, blood pressure greater than 140 / 90,

increased blood triglyceride concentration, central obesity (BMI greater than 30) and

increased amounts of urinary albumin.

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Gastrointestinal Medicine and Nutrition week 9 summary

Nutrition Requirements for Health

Every person that is living requires a certain amount of nutrition to survive. The human body

requires food for three broad functions. The nutrition is used for structural and functional purposes

such as maintenance of the BMR. Secondly any excess is used for performance that can be used for

aspects such as growth and pregnancy. The final purpose that

the food is used for when there is excess is being placed into

reserves, this outcome obviously has some major side effects.

We get nutrition into out body through eating and using the GI

tract to digest the food. Sometimes a person may be

incapacitated and food is then fed intravenous, or a tube is

passed through the mouth directly into the oesophagus. When

you are intravenously injecting somebody with nutrition you

must be careful that the osmolality of the vein as the increased

solutes may be harmful to the health of the vein.

The guidelines and the nutrient reference values are based on many different sources of

information including: dietary intakes for the population, observation of the population, animal and

human experimentation, other countries values, and many other sources. The 2003 NHMRC dietary

guidelines are split into adults and children. For adults the 4 guidelines are:

1. Enjoy a wide variety of nutritious foods

2. Prevent weight gain: be physically active and eat accordingly to your energy needs

3. Care for your food: prepare and store safely

4. Encourage and support breastfeeding

For the children and adolescents the guidelines differ slightly different:

1. Enjoy a wide variety of nutritious foods

2. Children and adolescents need sufficient nutritious foods to grow and develop normally

- Growth should be closely checked regularly for young children

- Physical activity is important in all children and adolescents

3.

4. Encourage and support breastfeeding.

Under each of these guidelines there are more specific rules that are set out to make them clearer.

For example under the first guideline for both the children and adults has:

- Eat plenty of vegetables, legumes, and fruits

- Eat plenty of cereals preferably wholegrain

- Include lean meat, fish, poultry,

- Include milks, yoghurts, cheeses and alternatives, (reduced fat milk for adolescents not

children as their energy needs are too high)

- Drink plenty of water

- Limit saturated fats and moderate fat intake

- Choose foods low in salt

- Consume only moderate amounts of sugar.

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There are currently new guidelines that are being worked on, however they are un-examinable. The

graphic educational tool that is being used to teach young children the correct quantities of food

that they are to consume has also changed recently. The previously popular pyramid has been taken

over by a plate to highlight the amount of each

item of food

they should

have on their

plate.

Dietary Energy

Basal Metabolic Rate: is the energy expenditure of a person who is lying down, completely at rest

both physically and mentally, in a thermo neutral environment with a person that has been fasting

for 12 hours. The person undertaking the test must be careful of the mental status of the patient

because people that are not mentally relaxed will be burning more energy. The resting metabolic

rate is a similar test however the qualifications are not as tight.

The energy unit that is used is the Joule (J) which is the energy expended to move 1kg, 1 meter by 1

newton force. The older unit that was used was the calorie; to convert from calories to J you simply

multiply by 4.184, normally in humans we are discussing in KJ for food consumption and MJ for daily

energy expenditure. The rate of energy

expenditure is in Watts (W) which is a measure

of J / sec.

The diagram right highlights the fact that there

is a lot of food that we are not able to gain

nourishment out of. The DM refers to dry

matter, the OM stands for organic matter. The

diagram below shows the amounts of food that

are usually absorbed by the body. It is shown in

the diagram that a small portion is always lost

in faeces, urine and heat. The Net energy is the

energy that is available to be used by the body for

maintenance, performance and if there are left overs

reserves. This shows us that about 90% of the food

that we eat being captured.

A typical male Australian diet has 40% protein and 30

% fat and the remainder being carbohydrate. With

fats saturated and unsaturated fat levels must be

watched.

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Fatty Acids: with fatty acids are the polyunsaturated fatty acids being omega 3 and omega 6. Omega

6 is the fatty acid linoleic acid and contains 18:2 formations. Omega 3 on the other hand is the

linolenic acid and contains the 18:3 formations. Vitamins also regularly come in through lipids; hence

the lipid is important as it is the only way that the vitamin can get across the membrane.

Known as Formation Digested to

Omega 6 Linoleic 18:2 Arachidoric acid (cell membrane)

Omega 3 linolenic 18:3 EPA (nervous tissue) and DHA (hormones)

Amino Acids: traditionally there are 9 essential amino acids, however histadine and arginine cannot

be created fast enough in a baby and hence needs to be ingested.

Reasons for malnutrition in a population include: poor education about nutrition, famine, illness

such as irritable bowel syndrome, abnormal diet (synthesising session), poverty, child neglect and

the elderly. These lead to deficiencies in the Amino Acid levels, and could be detrimental to the

health of the individual.

Minerals are potent organic compounds that are not used as a fuel source. For growth and health in

the human species they are essential however only minute amounts are required in the body. They

assist in many functional systems. There are two classifications of minerals:

- Minerals (moderate amounts needed): are Ca, P, Mg (all bone minerals), Cl, K, S Na

- Trace Minerals (trace amounts that are required: Cu, Al,

Sr (bone minerals, Co, Cr, Mn, Se, Fe, Zn

consume enough dairy products. Australians are also deficient in

Iodine, selenium iron and zinc. The table right highlights the amount

of each mineral there is present in a 60kg person. Below are

descriptions of the role of each of the minerals in the human body.

Iodine is essential for thyroid gland development

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Vitamins are also potent organic compounds that function as co-enzymes, and are not used as an

energy source ever. They must all be consumed except for vitamin D (from sunlight) and K (intestinal

bacteria produce it). Vitamins are divided into fat soluble and water soluble.

- Fat soluble vitamins include vitamins A, D, E and K. They are stored in the body except

for K. Vitamin A is generally associated with vision, D is from the sunlight and a

deficiency creates rickets, E is important for membranes, K is a bone regulator and a

blood clotting mechanism

- Water soluble vitamins: Vitamin B and C. Decreased levels of Vitamin C will create

scurvy, and the majority of vitamin C is found in the adrenal glands and the pituitary

gland.

Folate is very important for women that are pregnant as the folate is necessary for successful

development of the neural tube of the foetus.

- some final images of carbohydrates and the effect on the glycaemic index

Note:

The importance of appropriate nutrition and exercise will only get greater and greater as time goes

on. Currently 50% of Australians are considered overweight, and as a future medical practitioner it is

amount of chronic health problems in the future.

Scurvy is a disease that is caused from a lack of vitamin C it is very common in sailors where the

amounts of perishable fruits are low. It results is lethargy and malaise, then the formation of spots

on the skin, spongy gums and bleeding of the mucous membranes. When it advances there is a

risk of: wounds, loss of teeth, jaundice, fever, neuropathy and death. It is prevented and treated by

simply eating a diet that contains citrus fruits and vitamin C.

49 | P a g e

Guided Learning Session:

Activity 1: Nutritional requirements for pregnancy, lactation and Infancy

Listeria Monocytogenes is a problem in pregnant women and not usually other individuals.

The bacterium is in abundance in nature and affects pregnant women more because they are under

very different life circumstances. The bacterium is an infection that presents with influenza like

symptoms. The ultimate outcome for the patient is an early onset of labour, and reduced foetal

movements. Cooking food to above 70o C is wha

survive. Foods that are to be avoided include soft cheeses such as brie, camembert, feta, and queso

blanco fresco as they can be contaminated and permit the growth of the bacterium.

During pregnancy there are normal birth ranges in weight that a mother should put on.

For an individual with an ideal BMI an increase of body weight of about 25-25 pounds is the ideal

weight gain. For mothers that are starting overweight they are expected to increase less weight.

Individuals that are obviously underweight should put on a greater amount of mass. It seems odd

that although the baby only weighs 2.5 kg on average the mother puts on that much weight,

however, the amniotic fluid and the remainder of maternal modifications all add on weight. Mothers

of twins are supposed to increase weight in the 16 20 kg range.

Overweight and obese mothers place themselves and their children at risk of many

diseases. The mother is at risk of gestational hypertension, gestational diabetes. The newborn is at

risk of being overweight on delivery, being preterm and thus not being adequately mature for the

external environment, being a stillbirth, or having neonatal birth issues. Women that are obese and

are having children need to be careful and be in constant contact with their doctors.

Constipation may occur during pregnancy due to the decreased levels of physical activity

and a change in the diet that the mother undergoes. In order to overcome constipation, an increase

in the amount of non-starch polysaccharides should increase as those are what get broken down in

the large intestines.

Heartburn is caused due to an increase in the intra-abdominal pressure leading to the

stomach pressure also being increased through the decrease in size of the stomach space. The

uterus particularly in the later stages of pregnancy takes up a large space in the abdomen and the

stomach certainly becomes smaller. An increase in stomach pressure would obviously place pressure

on the upper oesophageal sphincter and this will result in heartburn. The consumption of smaller

regular meals can be advised to the patient to help the food be digested completely.

Preconception the parents should limit the consumption of apples, take .8mg folate

tablets, and follow the recommended food servings for every day. The avoidance of seafood is also

advised pre conception as seafood has the potential to be high in mercury which will in turn affect

the foetuses central nervous system development. The mother has no real need to worry about

allergen desensitisation for a newborn as there is no data to support it.

The consumption of solid foods from the infant should not be encouraged until 4 6

months after the baby is born. Until this time fluids and breastfeeding is the most important manner

for the Breastfeeding should be encouraged from the mother for a variety of reasons including:

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- The breast milk being a great energy source for the infant

- The act of breast-feeding is a great bonding experience to be shared between the infant

and the mother

- Breast milk contains IgA antibodies that are able to be passed to the body of the infant

through the bulk absorption in the small intestines

- Breast milk has a lot of the essential vitamins and minerals and amino acids in the correct

proportions for the newborn.

Activity 2: Nutritional Requirements for Infants, Children, Adolescents, and adults in Australia

An infant is defined as someone that is under the age of 12months. Child and Adolescent are in the

age groups 12 months to 18 years, and adults are over the age of 18. There are different nutritional

requirements for different age groups due to the different energy requirements of each. For

example adults require nutrition just for maintenance of their bodies, when children require it for

this function and the growth and development that they undergo. The table below highlights the

required percentages of each food intake for an adult. For children (up to a certain extent) food

intake should not be restricted due to the energy requirements for growth.

Lower Upper

Carbohydrates 45% 65%

Fats 20% 35%

Proteins 15% 25%

On top of this it is crucial that individuals get adequate vitamins and minerals so that the bodily

functions can continue. The typical Australian diet has some insufficiencies in vitamins and minerals:

calcium, sodium, selenium and iron are usually insufficient.

Dietary Guidelines for Adults

1. Eat a wide range of foods

2. Limit intake of foods and drinks containing saturate and trans fats, added salt, added sugar,

and alcohol

3. Achieve and maintain a healthy weight choose nutritious foods over that suit for energy

requirements

4. Encourage and support breastfeeding

5. Care for your food; store and prepare carefully

Gastritis: the inflammation of the lining of the stomach. Gastric Atrophy: is the end of chronic

gastritis, mucosal glands eventually losing function. Both of these increase in prevalence with

increasing age. A blocking of the stomach glands to would mean that the stomach and the remainder

of the gastrointestinal tract will be a lot less efficient at absorbing food.

National Physical Activity Guidelines:

- Think of movement as an opportunity not an inconvenience

- Be active every day in as many ways as you can

- Put together at least 30mins of moderate to vigorous intensity physical activity on most

days

- If possible enjoy some regular vigorous physical activity.

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Important diseases that is associated with obesity

- Coronary Heart disease

- Type 2 diabetes

- Hypertension

- Stroke

- Low back pain

- Gout

- Venous insufficiency

- Gestational diabetes

Synthesising Session: Evaluation of selected Dietary plans

Are vegetarian diets healthier? What about Vegan Diets?

A properly planned vegetarian diet is by and large a lot healthier for the individual.

disease. Protein inadequacies is the biggest concern to a vegetarian however with appropriate

planning it is able to get all the essential amino acids that you require through the diet.

Veganism is the abstaining from the use of any animal product. Vegans do not only stop

consuming meat and fish but do not consume any animal product including dairy products, eggs and

often honey. In general Vegans have a lot lower chance of chronic disease, however this can be

attributed to psychosocial factors as well as their diet. A well planned Vegan diet is able to produce

adequate amounts of all nutrition required.

Dr Atkins Diet plan

The atkins diet is based on the core principle of reducing the amount of carbohydrates and

slightly increasing fat quantities that are consumed to ensure that the body becomes more efficient

as burning fats for fuel. The process of fat breakdown known as ketosis, is at its highest when blood

insulin levels are low, and insulin levels are low when blood glucose levels are low.

There are four phases in the Atkins diet:

1. Induction phase is the most restrictive phase of the Atkins diet. For a period of two weeks

nearly all carbohydrates are cut with the purpose being to get the body used to processing

fats for energy. During this stage the most rapid weight loss is seen.

2. Ongoing weight loss: involves an increase in the amount of carbohydrates that are

consumed however, not to an extent where weight gain ceases. This phase of the Atkins diet

is continued until the individual is 10 pounds away from the target weight. This stage of the

diet has a weekly rung system where you slowly introduce certain things that you would

want to be in your normal diet, on a weekly intervals. The rungs in order are: induction of

acceptable fruit and vegetable, fresh cheese, nuts and seeds, berries, alcohol, legumes,

other fruits, starchy vegetables, and whole grains. A rung on the ladder can be missed if you

3. Pre-maintenance: carbohydrates are increased by another 10 grams per day, and the weight

loss is extremely slow

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4. Maintenance: is where all the habits that have been accumulated over time know have to

set in and you individual should attempt to maintain the health weight goal that they set out

to achieve.

High protein diet: is a special diet that is used by bodybuilders often in an attempt to build up

muscle and reduce fat simultaneously. The diet may include protein supplementation to ensure that

the appropriate amount of amino acids into the diet to assist muscle repair. Excess amounts of

protein associated with low carbs, particularly non starch polysaccharides, is very harmful for the

body.

Mediterranean Diet: is a diet that is based on the apparent paradox that is present between the high

level of fat consumption of some European countries and the lower rates of cardiovascular problems

in these countries. What the Mediterranean diet is based on is high consumption of fruits and

vegetables along with slightly higher fat consumption.

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Gastrointestinal Medicine and Nutrition week 10 summary

Nutritional Status Assessment

When you are discussing the Nutritional Status Assessment you are considering malnutrition.

Malnutrition can be considered for both an excess and deficit of energy, nutrience, and imbalance in

the requirements that are required for survival. Under nutrition is the deficit in energy and nutrition.

Over nutrition is the excess energy or nutrience. There are 4 methods of Nutritional Assessment:

1. Historical Information: using a nutritional diary

2. Physical Examination: skin folds, waist measurements

3. Anthropometric Data: is a non-invasive measurement of body parameters (BMI height and

weight)

4. Laboratory Test: look into other parameters (blood, urine, faeces)

Have to remember that there are limitations to the measurements of skin folds and BMI. Firstly the

people that are undertaking the measurements are not trained, the BMI is good for normal

individuals however, people that have larger muscle mass will wrongly represent a person health.

A primary nutritional deficiency is when there is inadequate nutritional

being ingested, whereas a secondary nutritional deficiency is when you

issue than lifestyle related issue for the primary nutritional

deficiencies. Through either of these issues you get a decline in

nutritional stores, leading to decreased body function and eventually

physical signs and symptoms. A physical examination is able to pick up

on the changing signs that the person is showing however the declining

nutrient stores and the decreased body function requires

laboratory test usually.

Anthropometric Data: include things such as growth charts

(refer Centre of Disease control as well as WHO growth

chart). The age : weight growth charts are useful for

understanding how well somebody is growing. The BMI for

boys aged five to nineteen is shown right, with the

percentiles on the right hand side of the graph.

Laboratory Test are most commonly blood and urine, and

they have the advantage over the other means of testing as you can gain the nutritional status

directly. They tell the physician information regarding electrolyte balance, acid base balance, organ

function, and problems with nutritional implications. However laboratory tests do have certain

limitations, the data is open for interpretation, with a single test being insufficient. With blood tests

the effects of the short term can have large implications on the results of the test. An example of a

laboratory test is the: protein-energy malnutrition (PEM). PEM works on the assumption that the

liver secretes certain enzymes that are found in the blood, and then by the levels of these proteins

that are present you are able to determine whether the liver is functioning appropriately. Protein

levels can also be checked through the urine, where the nitrogen balance can be tested through

urinary urea. Some different proteins that are found in the body are shown right with the half-life of

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each also shown. The half-life of a protein is the duration of

time that the protein remains is the body before it is broken

down.

Fats are the next nutrient that can be tested. Excess

levels of body fat have been associated with a lot of different issues in the body such as

cardiovascular disease and type 2 diabetes. It is important to note the distribution and the amount

of fat that is present on the body. Fats that are stored in and around the vital organs are a lot more

dangerous to the person than fat that is stored on the extremities. Lipid transport proteins such as

chylomicrons, VLDL, LDL, and HDL also can tell the physician the health of the individual in regards to

fat transport through a simple blood test.

Glucose Test are used to test for type 2 diabetes, and other glucose related absorption issue.

A normal blood test should show glucose concentration in between 4 and 8 mM. High levels of blood

glucose could simply be an instantaneous situation such as after a big meal. Urinary glucose diseases

such as glycosuria, then you cannot get rid of glucose out of blood stream meaning that you either

have a receptor problem or an insulin problem. With glucose testing, fasting blood glucose test is the

test that should be used twice to make sure. People that have glucose maintenance issues, generally

carry their own gluco-metres, and that is what tells them whether they should be consuming extra

foods or if their blood glucose is in a healthy realm. The HbA1c is a test that measures the long term

glucose levels (over a couple of months) so that people

cannot fix their results before blood tests. With the

HbA1c measurement; 6% is good, 8% is a warning, 10%

is bad, and 13% is dangerous, however recently to

decrease confusion; an mg / 100 mL level.

Vitamin and Mineral deficiencies are also an issue in Australian families, as many pe

fruit or vegetables. The other reasons for mineral deficiencies are poor absorption and abnormal

metabolism.

Non Nutritional related anaemia include: massive blood loss, infections, hereditary blood

disorders such as sickle cell anaemia, and chronic liver disease. Iron deficiency Anaemia is the other

type of anaemia. To test for this you get a blood count of: haemoglobin, haematocrit, serum ferritin

er than

normal, and serum folate is decreased and increased mean corpuscular volume or simply the mal-

absorption of the vitamins that can be checked through the schilling test.

GLS additions

Body Mass Index (BMI): is a method that is used to gauge the average health of a person of normal

build. The BMI is a measurement of your weight divided by your height squared, and it therefore in

the unit kg / m2. BMI is something that is inaccurate for people that are muscular build as the weight

factor in the calculation does not decipher between body fat and body muscle.

Skin Folds measurement: is another method that is utilised to determine the body fat percentage of

there is a manner to decipher between the muscle weight and the fat weight. A limitation to the skin

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folds measurement is that the measurements are only as accurate as the person that is taking the

measurements is trained. Another inadequacy in the testing of skin folds is that the test assumes

that the ratio of subcutaneous fat and deep fat stores is the same.

Waist to Hip Ratio: also assesses fat distribution. A high waist to hip ratio indicates high intra-

abdominal fat, which is considered to be associated with greater health risks.

Normal values for all three of the following tests is found in the GLS document and added in below.

BMI and waist/hip

Body Mass Index Values

Waist / Hip ratio

Underweight < 18.5 Female

Accepted weight 18.5 -24.9 Healthy < .8

Overweight 25 29.9 Male

Obese >30 Healthy < .9

Body Fat Percentage Averages

To calculate Body Fat percentage there

is an extremely complicated formula

that is shown right:

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GLS lecture: Dietary Records

Some of the methods that can be employed to record diet in a

population or on an individual level include:

- Weighed food record

- 24 hour diet recall

- Diet History

- Food Frequency Questionnaire (example shown right)

- Food Diary

Each of them has different respective advantages and disadvantages.

Advantages Disadvantages

Weighed food record

- Increased accuracy with portions

- Increased client burden - May alter the consumption

24 hour diet recall

- Low client burden - Avoids record keeping bias - More objective than Diet

history - Low cost

- Single recall may be different from usual diet

- Interviewer must be trained - Limited by client memory

(cognitive limitations of extremely young and the aged)

- Items are often forgotten

Diet History - Provides complete and detailed history

- Accounts for variations in diet - Representative of usual diet

- Requires a dietician to perform - Dependant on clients memory - Time consuming

Food Frequency Questionnaire

- Does not alter usual diet - Helpful for quick estimates - Helpful for describing food

intake patterns

- Foods may not be specific enough

- Does not provide enough information on total consumption

- High frequency of under and over estimation

Food Diary - Record of food intake at time of consumption

- Errors in recall are less than retrospective methods

- Food intake can be altered during reporting periods

- Under reporting is common (social desirability bias)

- Client burden is high - Portion size is difficult to

estimate - Number of days is required to

represent usual intake.

Some instructions that should be followed when you are keeping a food diary include.

- Record at time of consumption

- Include all beverages and snacks

- Provide as much detail as possible (include brand names)

- For composite dishes include the amount of each dish

- Keep food diary for 3 days with one being a weekend

- Try not to let it alter your normal diet

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In order to calculate the amount of nutrient that you are in-taking you can

utilise the values that are shown right.

1. Step one is to work out the amount of each of the individual food

groups you are consuming. You do this through the recording

mechanisms that are discussed above.

2. Step two, is to figure out the about of energy that you are in-

taking

3. Add the energy intakes together and then you have a baseline for total energy consumption

4. If you want to figure out % of energy intake you are getting from each food group you then

simply divide the individual food group by total and multiply by 100.

Other things that are recommended and should be noted

- Each person should intake 30 grams of fibre each day

- 1000 mg of calcium is advised daily

- Iron is advised in the diet: 18mg for women and 8 mg for men every day

In order to control your weight your energy intake should be equal to the energy expenditure. The

daily recommended energy demands are about

8700 Ki, and if you consume 2000-4000 K j per day

less than that you should lose about .5 1 kg.

- A big mac takes about 55 minutes of

continuous swimming to work off

Some examples of different foods and the energy

that is gained from them are highlighted below.

Synthesising Session: Assessing nutrition in day to day practice

As doctors we are always assessing the nutrition of the patients that we see, doctors assess

their patients in numerous different manners including those that are listed above and even some

things as simple as looking at the patient.

Monitoring Growth in Children:

Growth charts are to be used when you are assessing the efficiency of growth in children.

Growth charts are a great way to pick up issues such as protein-energy malnutrition, obesity or

overweight, and is incredibly good indicator for the doctor since different children grow at different

speeds. Growth charts are used in 5 different situations:

1.

Aiming to identify growh faltering which may indicate underlying physical ill health,

deprivation or neglect and allow early intervention

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2. As a surveillance tool for individual children in order to identify the onset of obesity early.

3. As a screening test at a single point in time to indicate abnormalities such as short stature,

or turners syndrome

4. As an eligibility criteria for growth hormone replacement

5. For analysis of population growth and trends.

When you are looking at certain case studies of individual that stop growing you need to take into

consideration their nutrition. There are three basic ways in which a person may be malnourished,

reduced intake of food, reduced absorption, or increased losses of energy / fuel.

Osteoporosis is a degenerative bone disease where increased activity of the thyroid gland

leads to hyperthyroidism and thus less calcium being deposited onto the bones. The lower levels of

calcium that is found on the bones then leads to the bones

becoming more brittle and in turn are a lot easier to

break. Vitamin D is an important factor in osteoporosis, as

vitamin D is crucial to help absorb calcium into the bones.

The risk factors for osteoporosis are shown on the right.

When a patient present with lethargy and a lack of

energy a potential reason could be some sort of anaemia.

In order to diagnose successfully the doctor must do a

blood count to test the amount of haemoglobin that is present and iron studies. Iron is transported

around the body with the molecule transferrin however multiple blood tests are required to gain an

accurate gauge of transferrin as it is also an acute phase reactant. So the main cause of anaemia

would be a lack of the consumption of Iron in the diet or an inability to absorb in efficiently.

are also at risk of getting these symptoms particularly straight after giving birth due to the large

amount of blood loss.

In summary when looking at the clinical assessment of nutrition you must take a

multifaceted view to ensure that nothing is missed. The issue is usually targeted to the person /

problem, and is often followed as a trend rather than a point reading.

-

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Gastrointestinal Medicine and Nutrition week 11 summary

Control of Food intake

The human body has numerous mechanisms within it that

ensures that the amount of food stores that are present stay

within a normal level. The body is either in a state of seeking

picture is highlighted in the image right, where food intake

control fits in. The control of food intake can be divided into three broad categories, psychosocial,

physiological and social or environmental. The diagram below

in the right highlights the numerous different factors that

religion and food availability must also be included in this very

broad umbrella. Here are some definitions for terms that are

- Hunger: to seek food with craving for food and

physiological effects such as restlessness and stomach

contractions

- Satiety: is the feeling of satisfaction after eating food,

to some extent a conditioned reflex

- Appetite: desire for food. Powerful and poorly

controlled stimulus to eat.

The control of appetite is numerous circulating peptides and steroids that have a powerful action on

the hypothalamus. The main sources of these controlling factors are the: fat cells, the

gastrointestinal tract and the pancreas. Inside the hypothalamus there are neuronal centres that

participate in the control of food intake. The lateral nuclei are stimulated to increase feeding, the

ventromedial is your satiety centre and is therefore stimulated when your body wants to quench its

desire to feed. The paraventricular nuclei

are inhibitory and the dorsomedial nuclei

are stimulatory, with the arcuate nucleus

being the pivotal component that ensures

that everything works around it.

Arcuate Nucleus: receives signals

from multiple GI and adipose hormones. It

regulates the food intake as well as energy

expenditure, and is accessible from

circulating signals in the bloodstream. There

are two primary populations of neurons that

have either have a inhibitory or stimulatory

effect on food intake. POMC/CART

hormones inhibit food intake and increase Energy expenditure while ARGP/NPY hormones stimulate

food intake and therefore inhibit energy expenditure. These hormones act as targets for several

other appetite regulating hormones such as leptin, insulin, CCK, and ghrelin. On top of these

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hormones there are a plethora of other

hormones that also have an impact on

the feeding and satiety levels of a

person.

Short Term control: preventing overeating at each meal

GI system will be unable to digest food at an optimal rate. Eat

smaller portions to allow GI tract to allow passage at steady rate

to digest and absorb at an optimal rate. By eating the correctly

sized portions you also decrease the risk of getting too much

metabolic storage, through the over consumption of food.

Systems that are at work to limit short term control include:

- Distension of the stomach and the duodenum; stretch

receptors send inhibitory signals through the vagus nerve

to suppress feeding.

- Oral factors are also present: where when you chew food

the body has a counter on the amount of food that is

coming through.

With these control mechanism some people they do not work as well and then they are genetically

more associated to gain weight.

Gastrointestinal Hormones: there are hormones that are present in the body that act to both

suppress and stimulate feeding. Hormones that suppress feeding include:

- CCK (responses to fat/protein in the duodenum): sensory receptors in duodenum send

messages through the Vagus nerve to the brain that satiety has been reached

- Peptide YY: secreted from the entire GI system (mainly the ileum and the colon) is

stimulated by the food intake and influenced by calories and food composition. The higher

levels of calories the greater the secretion of the peptide YY

- Glucagon like peptides are secreted due to a food in the intestines they stimulate glucose

dependant insulin to be secreted which suppresses appetite

Hormones that increase the need to feed include

- Ghrelin: which is released by the parietal cells (small amounts by the intestines) in response

to fasting it stimulates body to want to eat more food by increasing its appetite. The exact

method that it uses is unclear.

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Long term control: maintenance of energy stores

When the body is looking at long term control of the energy stores there are basically two

situations that it can be in. Firstly it could be in a state where energy stores are below normal and in

this state the body will increase its feeding. Or it could be in a

state of high energy stores when feeding is decreased. The

long term control also has a lot to do with the past situation

the body was in. After starvation the body is more likely to

have the desire to eat large quantities of food, and after

times of high feed levels, the body will generally eat less. The

concentration of blood metabolites play a crucial role in this mechanism with glucostatic amino

factor that the body takes into account, when in a cold climate people generally eat a lot more in

order to maintain a higher standard of body warmth.

The feedback mechanism that is in place involves the hormone leptin. Leptin is a hormone

that is secreted from the adiposities of the body, when the levels are high. Basically when adipose

tissue levels are high there are high levels of leptin that is secreted which in turn decreases hunger

and then decreases fat storage. Leptin is also related to the onset of puberty in women, as when

adequate leptin is present the person has adequate fuel storages to undergo the changes that are

undertaken during puberty. There are mutations that cause a defect in leptin receptors, and

mutations that cause you to be unable to produce leptin. When this occurs the person wants to eat

a lot, as there is no feedback to stop people from being aware of the amount of adipose tissue that

they have. This can lead to morbid obesity or hyperphagia (abnormal amount of eating).

All these mechanism are present in normal people when they are in a healthy body weight

range. However with people that are not in a healthy body weight, then they may lose the ability to

control their weight. In obesity situations these mechanisms are overcome. One of the largest issues

with people that are obese is the pleasure system in the brain. Dopamine is a drug that gets

released from the body after pleasurable experiences; it makes you feel good and makes you want

to undertake the experience again. Dopamine is generally secreted from the body after things such

as sexual intercourse, exercise, and in some people eating.

When eating becomes a pleasurable experience the quantity

of food that is consumed by that person will obviously

increase, increasing their body weight. This is how people get

addicted to foods or most activities in that manner.

Peripheral Signalling: at the level of the

Gastrointestinal system feedback is created through the

vagal reflexes and the GI peptide hormones. At a peripheral

level the feedback mechanism is based around the presence

or absence of energy stores.

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Mouse Models looking at obesity and diabetes

Using parabyosis experimentation they joined multiple mice together so that they share the same

blood system, and genetically modified them to be an obese mouse, a diabetic obese mouse or a

normal mouse. The results of the parabyosis experiment are shown right the explanation was gained

that:

- The db gene coded for

the leptin receptor

- The ob gene coded for

leptin

Using these assumptions that

are listed above, it is easy to

understand the results. When

leptin was given to the mouse

that was unable to produce leptin, the weight went back to normal, however in the mouse that

lacked the leptin receptor nothing could have been done.

GLS additions

The control of food intake can be physiological as it is described above, however it can also be

psychological or behavioural. When individuals undergo extreme periods of dieting they are often

cognitively impaired, and develop different behavioural traits. There were two diets that were

looked at in the GLS: firstly the women from Antibes and their extreme diet; take note of the

outcome of the crash dieting, the second was of a group of young healthy men and their highly

restrictive diet that they had to undergo. The specifics of the diets include:

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The women of Antibes:

The starvation of the men: 36 young strong psychologically strong men were put on extremely

restrictive diets for 6 months. For three months the individuals are normally, while their lifestyles

were studied carefully. After this 3 month period the candidates went through 6 months of a diet

where their calorie intake was approximately halved. The body weights of the individuals dropped

by on average 25%. After the 6 month diet the men went through a 3 month rehabilitation phase.

There were many physical, psychological and social changes during the diet period, and some were

even maintained during the recovery and even after recovery. There were changes in:

- Attitudes and Behaviour towards food: food becomes the primary topic of conversation, and

dreams. There was decreased desire for sexual activity during semi-starvation. Men began to

eat different concoctions of food, and collect items that were related with food such as cook

books and cooking utensils. They were torn between gulping their food down rapidly and

making it last a long time.

- Binge Eating: several of the volunteers were unable to stick to the guidelines and went off

and had copious amounts of food. There was incredible complaints of hunger from nearly all

the men. During the rehabilitation phase a lot of the men could not control their urges, and

would eat amounts of food that were so large that they would fall ill. Others would have to

geographically isolate themselves from the food, otherwise they would not be able to stop

themselves from eating.

- Social and Sexual changes: the men became slowly more withdrawn and isolated.

- Cognitive and physical changes

The experiment proved that many of the previous symptoms that were associated with anorexia

nervosa, were actually associated with starvation and not anorexia. Giving people with eating

disorders may find the results of this experiment useful, as they are able to understand the

reasoning behind the feelings that they are experiencing.

(Read through the readings and summarise the diets and the results, look through GLS answers).

Synthesising Session Adolescent Eating Disorders

Adolescent eating disorders are not limited to adolescent people, adults are able to contract

the illness as well, however adolescence is the usual time for these behaviours to occur, as during

your teenage years you are normally under educated in the decisions that you make in regards to

their diet. An eating disorder is a severe illness causing more illness (time away from study / work)

and death than most other illnesses that affect young people. It was large tolls on not just the

physical nature of the affected, but the emotional state of themselves and those that are around

them. Eating disorders are not simply an alternate way of life, or a bad behaviour, people seem to

use the word loosely when in reality it is a very serious issue.

There are many eating disorders that effect adolescents, they effect at both ends of the

eating scale. Firstly there are Binge Eating disorders, that effects 5:100 people. The other end of the

scale involves disorders such as Anorexia Nervosa and Bulimia Nervosa where the body is incredibly

underweight. The most common eating disorder is EDNOS (eating disorders not otherwise specified)

as they have not been specified.

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Anorexia Nervosa: is the relentless self-starvation and severe loss of weight, with mental

attributes as well such as denial of the severity of the situation and the fear of weight gain.

Individuals with anorexia nervosa have weight and shape concerns that are severely more acute

than normal, and they view a distorted body shape as ideal. They commonly indulge in other

methods to lose weight such as: laxatives, self-induced vomiting, and excessive exercise. There are

sometimes episodes of binge eating, and severe levels of mood changes with depression and anxiety

risk high. A person with anorexia nervosa is less than 85% of their expected body weight, whereas a

person with anorexia bulimia is normally within 10% of their weight range. People with anorexia

nervosa have large amounts of what is the appropriate body image, they are able to look at healthy

people and know that they are healthy, yet still think that they are very overweight. 5% of people

with anorexia nervosa pass away within the first 10 years, it is one of the hardest diseases to treat as

there is a physical as well as a psychological issue that has to be faced by the allied heath team.

With anorexia bulimia the person may even be overweight as they go through binge eating

that is followed by vomiting.

A lot of people believe that the disease of anorexia is new, however there is well

documented evidence of people that are anorexic many years ago, however the 20th century

be noted that only 1 in 10 individuals that suffer from anorexia are males.

Since the turn of the industrial revolution and definitely in recent times rates of obesity and

overweight individuals has been going higher and higher. In Australia alone 56% of adults are

considered obese and 20% of children. The issue with obesity is a lot more prevalent than that of

too much of a change.

People that are at the highest risk of getting obesity are city dwellers, women that were

expose

people with low self-esteem however are driven to achieve. The media plays a role as it promotes

Once a person is affected by anorexia nervosa a team including

nutritionists, doctors, psycho-therapists, nurses and supportive family

members are crucial to ensure that the individual survives. There are 4

steps that must be overcome highlighted in the image right.

Binge eating is another eating disorder that is a lot more common in

men. Some lifestyle characteristics that influences the binge eating include: low self-esteem,

depression, body image concerns, and poorly controlled diabetes. If somebody is binge eating you

must put them on a moderat

they would then be at a much higher chance of relapsing.

Another issue with people that suffer from eating disorders is that they are very rarely able

to self-diagnose. The majority of the time that they present is because they have been told to by a

family member or have been forced to by a family member.

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The difference between bulimia and anorexia is that in bulimia there is the constant cycle of binge

eating and then vomittng, whereas in anorexia there is simply a mass restriction in the amout of

food that is consumed.

It must be remembered that not all people that diet have an eating disorder.

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Gastrointestinal Medicine and Nutrition week 12 summary

Diet and Disease Management

GIMN week 12 intro lecture is un-examinable

There is a strong correlation between diet and disease in life. Diet and nutrition play an important

role in promoting good health, growth and development during life. It must be noted that both

under-nutrition and over-nutrition have negative impacts on the effects of chronic disease. Diseases

that present the greatest public health issue due to poor diet and nutrition include: obesity,

diabetes, Cardio vascular disease, cancer (colon), osteoporosis, and dental disease. Chronic disease

accounts for an enormous amount of deaths (75% by 2020) in the community and more than half of

chronic disease deaths are related to poor nutrition. Chronic diseases are largely preventable in the

community if people make different lifestyle choices, such that diets that contain 5-9 serves of fruit

per day decrease the risk of all chronic diseases.

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Ecology of

Health