biol 1203 week 2_ls_s15_students (1)

Biology 1203 Week 2

Diges2on I & II Diges2on Lab

Diges2ve anatomy lab Part 1: Locate and describe func2on of primary and accessory diges2ve organs

Explain how a hamburger is digested

Part 2: Demonstrate competency with the microscope Iden2fy major parts of microscope

as in Biol 1103 Histology of diges2ve system

DIGESTIVE SYSTEM What are the main processes that occur?

1. Describe the rela2onship between the following processes in gastrointes2nal system: inges0on, diges0on, absorp0on, defeca0on

2. Dis2nguish between extracellular diges0on and intracellular diges0on

Learning Objec2ves Anatomy & Physiology of the Diges2ve System

3. Describe the anatomy and func2ons of the: a. Buccal cavity (deglu22on) e. Pancreas

b. Esophagus f. Small intes2ne

c. Stomach g. Large intes2ne (defeca2on)

d. Liver (connec2on to gall bladder and its blood supply)

2013 Pearson Educa2on, Inc.

1. Ingestion

2. Digestion

3. Absorption

4. Defecation

Food

Pharynx Esophagus

Stomach

Lymph vessel

Small intes2ne Large intes2ne

Blood vessel

Feces

Anus

Processes in the diges2ve system 1. Inges0on

The process of taking food/liquid into the mouth

2. Diges0on Breakdown of food into

smaller pieces Mechanical: physical

breakdown (e.g., teeth) Chemical: breakdown of

molecules using enzymes 3. Absorp0on

Movement of digested products into the lumen of the GI tract, then into lympha2c and circulatory system

4. Defeca0on Elimina2on of indiges2ble

substances, wastes, bacteria, and unabsorbed substances

Extracellular Diges0on Food processing in the

diges2ve system OUTside cells by enzymes

produced by the diges2ve tract cells & glands

Plasma membrane

Phagocy0c vacuole

Diges0ve enzymes

Diges0on

Lysosome

Intracellular Diges0on Phagocy2c ac2vity of

white blood cells INside cell by enzymes of

lysosomes

Dis$nguish the 2 processes and give an example of each

DIGESTIVE SYSTEM Loca2on and general overview

1. Describe the rela2onship between the following processes in gastrointes2nal system: inges0on, diges0on, absorp0on, defeca0on

2. Dis2nguish between extracellular diges0on and intracellular diges0on


3. 9. Describe the anatomy and func2ons of the:

a. Buccal cavity (incl. deglu22on) e. Pancreas

b. Esophagus f. Small intes2ne

c. Stomach g. Large intes2ne (defeca2on)

d. Liver (connec2on to gall bladder and its blood supply)

The Diges2ve System

Divided into two groups of organs: Gastrointes0nal (GI) tract Accessory diges0ve organs

Right lateral view of head and neck and anterior view of trunk

Tortora Figure 24.1, pg 968

Mouth (oral cavity) - contains teeth and tongue Paro$d gland

(salivary gland)

Stomach Pancreas

Large intes2ne Rectum Anal canal Anus

Esophagus Liver

Small Intes2ne Gallbladder

Diges2ve System

Layers of the GI Tract

Artery

2. SUBMUCOSA

3. MUSCULARIS: Circular muscle Longitudinal muscle

4. SEROSA: Areolar connec2ve 2ssue Epithelium

Muscularis mucosae

1. MUCOSA: Epithelium Lamina propria

Nerve

4 layers Mucosa structurally varies most

between organs protec2ve stra.ed squamous epithelium

(outer organs); simple columnar epithelium for absorp2on/secre2on (inner organs)


BUCCAL CAVITY Anatomy and role in diges2on

Anterior view Tortora Figure 24.5, pg 975

Lips

Tongue (lifed upward)

Opening of duct of submandibular gland

Hard palate

Sof palate

Uvula

Cheek

Teeth

The Buccal Cavity

The Buccal Cavity Func2ons

Teeth: mas0ca0on to reduce par2cle size Tongue: skeletal muscle moves food around the buccal

cavity mixing it with saliva to form bolus and contains taste receptors

Saliva: secreted by salivary glands (1-1.5L/day) 99.5% water; 0.5% solutes (mucus, ions, bicarbonate, salivary amylase, lysozyme, dissolved gases)

Func2ons: Ini0al diges0on of starch in the mouth (amylase) Generally keeps mouth

moist and clean

The feel, taste, smell, sight, sound or thought of food can also promote saliva2on (cephalic phase of diges2on)

Starch Maltose

salivary amylase

... ...

Paro2d duct

Opening of paro2d duct (near second maxillary molar)

Second maxillary molar tooth

Tongue (raised in mouth)

Lingual frenulum

Sublingual ducts

Submandibular duct

Mylohyoid muscle SUBMANDIBULAR GLAND

PAROTID GLAND

Lesser sublingual duct

SUBLINGUAL GLAND

Loca2on of the major salivary glands


ESOPHAGUS Anatomy and func2on

2013 Pearson Educa2on, Inc. Microscopic structure of the esophagus.

Mucosa (stra2ed squamous epithelium)

Submucosa (connec2ve 2ssue) Lumen Muscularis externa Circular layer Longitudinal layer

Adventitia (brous connec2ve 2ssue)

Marieb Figure 23.12a, pg 862

The esophagus Posterior to larynx

Runs from pharynx to stomach (25cm)

Upper and lower esophageal sphincters

The esophagus Transports food to the stomach through the ac2on of peristalsis (4-8s)

Upper and lower sphincters that relax during swallowing Regulate the passage of food into and out of the esophagus

No enzymes are secreted in the esophagus Salivary amylase con2nues to digest carbohydrates

Does any diges$on occur in the esophagus?

Peristal2c movement

Recall that the GI tract has 2 layers of muscle In a sec2on of the tract, circular muscles contract, squeezing the tube

At the same 2me in the sec2on inferior to the circular muscles, the longitudinal muscles contract, widening tube and shortening it

These two ac2ons proceed, sec2on by sec2on down the length of the tube

Be able to briey describe the process of peristalsis in your own words


Deglu22on (swallowing) Bolus of food

Tongue Pharynx Epiglojs Glojs Trachea

Buccal phase 1

Uvula Bolus EpigloUs

Esophagus

Pharyngeal phase

Esophageal phase

Esophageal phase contd

Esophageal phase contd .

Relaxed muscles Circular muscles contract Bolus of food

Longitudinal muscles contract

Gastroesophageal sphincter closed

Relaxed muscles

Circular muscles contract

Gastroesophageal sphincter opens

Upper esophageal sphincter Bolus

2

4

3

5

Stomach

Marieb Fig 23.13; pg 864

Upper esophageal sphincter

Prac2ce Ques2on 1

Gastroesophageal reux disease (GERD) What happens? Inadequate closure of the lower esophageal sphincter (LES)

Contents of the stomach move up (reux)

Why is this a problem? Low pH due to hydrochloric acid burns the unprotected esophageal wall (heartburn)

What is the cause? Alcohol, caeine, smoking

How are the symptoms controlled? Diet and medica2ons

STOMACH Anatomy and func2on

Greater curvature

Lesser curvature

Anterior view of regions of stomach

PYLORIC ANTRUM

CARDIA BODY

FUNDUS

PYLORIC CANAL

Pyloric sphincter

Duodenum

Esophagus

Lower esophageal Sphincter (LES)

PYLORUS


Stomach Car is Fun 0l Bodies Pile

MUCOSA

SUBMUCOSA

MUSCULARIS - 3 layers

Gastric pits

SEROSA

Lumen of stomach

Three-dimensional view of layers of stomach


Stomach layers

Gastric pit cell types and secre2ons

Gastric lipase

Gastric juice: Hydrochloric acid (HCl) Enzymes pepsinogen gastric lipase

Hormones - gastrin

Proteins Pep2des pepsin

Stomach Chemical Diges2on

pepsinogen

HCl N C

N C N C

Triglycerides (or diglycerides) Monoglycerides + Fapy Acids

gastric lipase

Triglycerides Diglycerides + Fapy Acids lingual lipase HCl

Why does the stomach not digest itself?

Pepsinogen secreted in inac0ve form of enzyme (low pH of acid ac2vates it pepsin) Mucous barrier containing bicarbonate (basic) ions to neutralize acid Rapid cell divisions replace damaged cells

Func2ons of Stomach Component Func0on

Lumen Food storage Smooth muscle Mechanical diges2on through mixing waves Gastric juice Hydrochloric acid (HCl):

oAn0bacterial oDenatures proteins oAc2vates pepsinogen oAc2vates lingual lipase

Pepsinogen: precursor of pepsin Pepsin: protein-diges2ng enzyme Gastric lipase

Endocrine glands Hormone gastrin s2mulates release of gastric juice Pyloric sphincter Regulates passage of food to duodenum Result: Chyme

Summary Diges2ve system consists of GI tract (~ 9m long tube open

to the external environment; 4 2ssue layers) and accessory organs that aid diges2on

Following inges2on: food is broken up in the oral cavity by mas2ca2on and saliva secre2on (including mucus and amylase) to produce a sof bolus of food for swallowing (deglu22on)

Deglu22on consists of 3 phases in which the bolus moves from mouth to stomach via the pharynx and esophagus

Stomach stores, churns and mixes food with (acidic) gastric secre2ons to produce liquid chyme to pass to the small intes2ne through pyloric sphincter; some protein and lipid diges0on occurs here but minimal absorp2on (water, ions, short chain FA, alcohol)

Prac2ce Ques2on 2

ACCESORY DIGESTIVE ORGANS Anatomy and func2ons of liver, gall bladder, pancreas

The small intes2ne is where the bulk of diges0on and absorp0on occur

However, we must rst cover several essen2al accessory diges2ve organs, as their role is important for the proper func2oning of the small intes2ne Liver Gall Bladder Pancreas

Accessory diges2ve organs

Falciform ligament

Diaphragm

Anterior view Tortora Figure 24.15, pg 989

Right lobe of liver

Lef hepa2c duct Right hepa2c duct

Cys2c duct

Gallbladder

Duodenum

Hepatopancrea0c ampulla (ampulla of Vater)

Common bile duct

Common hepa2c duct

Pancreas

LeZ lobe of liver

Pancrea0c duct

Liver

Pancreas Func0ons I. Diges2on (as an exocrine gland; 99% cells)

Pancrea2c juice: diges2ve enzymes and bicarbonate

II. Metabolism (as an endocrine gland; 1% cells) Glucose-regula2ng hormones: insulin and glucagon

Be able to describe these enzymes and know the site of ac$on

Diges0ve enzymes: Carbohydrates: pancrea0c amylase

(starch to maltose) Lipids: pancrea0c lipase (lipids to

triglycerides) Proteins (secreted in inac2ve form):

trypsinogen, chymotrypsinogen, procarboxypep0dase, proelastase (all digest proteins to pep2des)


I. Diges2on i. Produc2on of bile salts

II. Metabolism i. Catabolism (breaking down of substances)

a. Hemoglobin (producing bilirubin) b. Amino acids (producing urea) c. Hormones

ii. Anabolism (synthesis of substances) a. Plasma proteins b. Glycogen

iii. Storage a. Glucose (as glycogen) b. Fat-insoluble vitamins (A, D, E, K) c. Some minerals (Cu, Fe)

III. Detoxica2on of foreign substances (alcohol, drugs)

Liver Func2ons

Oxygenated blood from hepa0c artery

Right atrium of heart

Nutrient-rich, deoxygenated blood from hepa0c portal vein

Inferior vena cava

Liver sinusoids

Hepa2c vein

Central vein

2

3

4

5

6

1

Hepa2c blood ow


Importance of hepa2c portal system

Allows modica2on of nutrients absorbed from the diges2ve tract by the liver cells

Liver removes toxins from the blood and adds plasma proteins

Controls nutrients and substances entering the rest of the circulatory system

Gall bladder

Small pear shaped sac tucked into anterior inferior surface of liver

Stores and concentrates bile salts Bile released into the duodenum of the small intes2ne

Liver, Gall Bladder and Pancreas Connec2on with the Duodenum

Ampulla of Vater

Pancrea0c duct & duct of Santorini

Accessory Organs: Review quiz

Which organ produces bile? Which duct carries bile to the small intes2ne? Which organ plays an important role in energy metabolism?

Why does pancrea2c juice contain bicarbonate?

SMALL INTESTINE Anatomy and func2ons

Small Intes2ne Gross Anatomy

Duodenum

Jejunum

Large intestine

Ileum Rectum Jejunum

Func2ons of small intes2ne Produces intes2nal juice

Bicarbonate ions: further neutraliza2on of acidic chyme Mucus: for further lubrica2on

Most important site of chemical diges0on Comple2on of diges2on Produces diges2ve enzymes for carbohydrates and proteins (brush-

border enzymes) NB. Diges2ve enzymes from pancreas and bile (from liver) mix with

intes2nal juice in small intes2ne to aid diges2on

Absorp2on of 90% nutrients and water

Releases secre0n and cholecystokinin hormones s2mulate pancrea2c juice and bile release

Large surface area of small intes2ne enhances nutrient diges2on and absorp2on

Circular folds

Great length of small intestine

Brush border (with digestive enzymes)

Microscopic anatomy of small intes2ne

Marieb Figure 23.22, pg 876

Chemical Diges2on in the Small Intes2ne Carbohydrates

maltase sucrase lactase

Brush-border enzymes of the intes2ne

Sucrose sucrase Glucose + Fructose

Starch Maltose

pancrea$c amylase maltase

Glucose ... ...

Lactose lactase

Glucose + Galactose

Chemical Diges2on in the Small Intes2ne Lipids

Triglycerides (or diglycerides) Monoglycerides + Fapy Acids

pancrea$c lipase

Emulsica.on Fat globule

Bile salt Fat droplet coated with bile salts

Chemical Diges2on in the Small Intes2ne Proteins

Proteins Pep2des

trypsin chymotrypsin

N C

N C

carboxypep$dase aminopepdidase

dipep$dase

Amino Acids

trypsin

chymotrypsin carboxypep$dase aminopep$dase dipep$dase

endopep2dases

exopep2dases

Pancrea2c enzymes

Brush-border enzymes of the intes2ne

N C

Ac2va2on of protein diges2ve enzymes

Released from the pancreas, ac2vated in the duodenum (small intes2ne)

Trypsinogen is converted to trypsin by enterokinase (found on the intes2nal wall)

Trypsin starts to digest proteins and also converts chymotrypsinogen to chymotrypsin and procarboxypep2dase to carboxypep0dase

Absorp0on of nutrients

Most nutrients (macronutrients, minerals, vitamins) and water (90%) are absorbed in the small intes0ne

2 stages to nutrient absorp2on from GI tract enter intes0nal cells lining villi, enter either the bloodstream or the lympha0c system

Nutrients to be absorbed take the following route from the lumen of the GI tract: Plasma membrane into the intes2nal cell Plasma membrane out of the intes2nal cell

Carbohydrate Absorp2on

Glucose and galactose

Fructose

Intes2nal lumen Intes2nal cell (with microvilli)

Blood (villus capillary to hepa2c portal vein)

Carbohydrate Absorp2on

Absorp2on into intes2nal cell: Glucose, galactose, mannose: ac2ve transport (secondary)

Fructose: facilitated diusion Leaving the intes2nal cell: Glucose, galactose, mannose, fructose: facilitated diusion

Route to the liver: Bloodstream, via the hepa2c portal vein

Be able to describe the diges2on, absorp2on, and transport of carbohydrates

Lipid Absorp2on

Lipid Absorp2on Absorp2on into intes2nal cell (detach from micelles): Short chain fapy acids: simple diusion Long chain fapy acids: simple diusion

Leaving the intes2nal cell: Short chain fapy acids: simple diusion Long chain fapy acids: rebuilt into triglycerides and combine with proteins (cholesterol and phospholipids) to form chylomicrons, which leave cell by exocytosis

Route to the liver: Short chain fapy acids (& glycerol): bloodstream, via the hepa2c portal vein

Long chain fapy acids: lacteal, lympha2c system (to thoracic duct to enter systemic blood circulatory system)

Be able to describe the diges2on, absorp2on, and transport of lipids

Absorp2on of Amino Acids

Facilitated

Intes2nal lumen Intes2nal cell (with microvilli)

Blood (villus capillary to hepa2c portal vein)

Protein Absorp2on

Absorp2on into intes2nal cell: amino acids, dipep2des, tripep2des: ac2ve transport (primary and secondary)

Leaving the intes2nal cell: amino acids, dipep2des, tripep2des: facilitated diusion

Route to the liver: Bloodstream, via the hepa2c portal vein

Be able to describe the diges2on, absorp2on, and transport of proteins

Lef subclavian vein

Heart Small short-chain fapy acid

Villus (greatly enlarged)

Chylomicron

Blood capillary

Lacteal Arteriole

Amino acid

Monosaccharide Venule

Blood

Lymph Lympha2c vessel

Hepa0c portal vein Thoracic duct

Liver

Figure 24.21, pg 1002

Transport of Absorbed Nutrients

Blood Monosaccharides Amino acids

Lymph Chylomicron

Diges2on and Absorp2on Review Quiz

1. Which enzymes are required to breakdown starch into glucose?

2. Name a way in which pepsin diers from aminopep2dase?

3. How is absorp2on of amino acids and monosaccharides similar? (Clue: transport mechanisms)

4. Why arent lipids absorbed into the blood? 5. Which blood vessel carries (nutrient-rich) blood

from the small intes2ne to the liver?

10. Describe the anatomy and func2ons of the large intes2ne.

11. Describe the process of defeca2on.


Appendix

Anterior view of large intes2ne showing major regions

Ileum


Rectum Cecum

Ileocecal sphincter (valve)

Transverse colon

Anal Canal Anus

The large intes2ne

Ascending colon

Descending colon

Sigmoid colon

Func2ons of large intes2ne

Absorp2on of some water, minerals and vitamins No diges2ve enzymes are secreted here Carry bacteria Digests some cellulose, protein, bilirubin Produces Vitamin K and bio2n

Forma2on of feces (stools) and defeca2on Feces = semisolid, contains water, inorganic salts, sloughed-o epithelial cells, bacteria, undigested materials, indiges2ble materials

Internal anal sphincter (involuntary)

Rectum

Anal canal

Frontal sec2on of anal canal Anal column Anus

External anal sphincter (voluntary)

Tortora Fig 24.23, pg 1007

Defeca2on

Defeca2on reex

Steps 1. Movement of the feces causes

distension of the rectal walls, which s2mulates sensory (stretch) receptors

2. In response, a spinal reex causes contrac2on of the rectal walls and opening of the internal anal sphincter

3. Voluntary signals from the cerebral cortex open the external anal sphincter and the rectum emp2es


The Diges2ve System Summary

1. Describe the chemical diges0on of the following nutrients, specifying the source and the func$on of the principal enzymes involved:

a) Carbohydrates b) Proteins c) Lipids

Learning Objec2ves Diges2on & Absorp2on of Macromolecules

2. Specify the end-products of the diges2on of the following and explain how they are absorbed:

a) Carbohydrates b) Proteins c) Lipids


Foodstuff Enzyme(s) and source Site of action Path of absorption

Starch and disaccharides

Oligosaccharides and disaccharides Carbohydrate digestion

Lactose Maltose Sucrose

Galactose Glucose Fructose

Salivary amylase

Pancrea0c amylase

Brush border enzymes in small intes2ne (dextrinase, gluco- amylase, lactase, maltase, and sucrase)

Mouth

Small intes2ne

Small intes2ne

Glucose and galactose are absorbed via cotransport with sodium ions. Fructose passes via facilitated diusion. All monosaccharides leave the epithelial cells via facilitated diusion, enter the capillary blood in the villi, and are transported to the liver via the hepa2c portal vein.

Summary of Diges2on and Absorp2on Carbohydrates



Protein digestion

Proteins

Large polypep2des

Small polypep2des, small pep2des

Amino acids (some dipep2des and tripep2des)

Pepsin (stomach glands) in presence of HCl

Pancrea2c enzymes (trypsin, chymotrypsin, carboxypep0dase)

Brush border enzymes (aminopep0dase, and dipep0dase)

Stomach

Small intes2ne

Small intes2ne

Amino acids are absorbed via cotransport with sodium ions. Some dipep2des and tripep2des are absorbed via cotransport with H+ and hydrolyzed to amino acids within the cells. Infrequently, transcytosis of small pep2des occurs. Amino acids leave the epithelial cells by facilitated diusion, enter the capillary blood in the villi, and are transported to the liver via the hepa2c portal vein.

Foodstuff Enzyme(s) and source Site of action Path of absorption

Summary of Diges2on and Absorp2on Proteins



Fat digestion

Unemulsied triglycerides

Lingual lipase

Gastric lipase

Emulsica2on by the detergent ac2on of bile salts ducted in from the liver

Pancrea0c lipases

Monoglycerides (or diglycerides with gastric lipase) and fapy acids

Mouth

Stomach

Small intes2ne

Small intes2ne

Fapy acids and monoglycerides enter the intes2nal cells via diusion. Fapy acids and monoglycerides are recombined to form triglycerides and then combined with other lipids and proteins within the cells. The resul2ng chylomicrons are extruded by exocytosis. The chylomicrons enter the lacteals of the villi and are transported to the systemic circula2on via the lymph in the thoracic duct. Some short-chain fapy acids are absorbed, move into the capillary blood in the villi by diusion, and are transported to the liver via the hepa2c portal vein.

Foodstuff Enzyme(s)

and source Site of action Path of absorption

Summary of Diges2on and Absorp2on Lipids


Diges2on Problem: Review of diges2ve enzymes Fill in the gaps

Macronutrient Diges0ve Enzyme

Source Site of ac0on Ac0on

Carbohydrate

Amylases Dissacharidases E.g. 4. __________

Saliva

3. __________ 5.___________

1.____________

Small intes2ne Small intes2ne

2._______

Dissacharide Monosaccharides

Protein

Pepsin Trypsin Chymotrypsin Carboxypep2dase Amino- and di-

pep2dases

Stomach 8. ___________ 8. ___________ Pancreas 10. __________

6.____________ Small intes2ne Small intes2ne Small intes2ne Small Intes2ne

7.___________ 7.___________ 7.___________ 9.__________ 9.__________

Lipid Bile salts Lipases

11.__________ 12. __________ Gastric Pancrea2c

Small Intes2ne Stomach Stomach Small Intes2ne

Fat (triglyceride) globules Fat droplets

13.__________ 13.__________

Diges2on Problem: Review of diges2ve enzymes Fill in the gaps

Macronutrient Diges0ve Enzyme

Source Site of ac0on Ac0on

Carbohydrate

Amylases Dissacharidases E.g. 4. maltase, lactase,

sucrase

Saliva 3. Pancreas

5. Intes$nal wall (BB)

1. Buccal cavity Small intes$ne Small intes$ne

2. Starch maltose Disaccharides monosaccharides

Protein

Pepsin Trypsin Chymotrypsin Carboxypep2dase Amino- and di-

pep2dases

Stomach 8. Pancreas 8. Pancreas Pancreas 10. Intes$nal

wall (BBE

6. Stomach Small intes$ne Small intes$ne Small intes$ne Small intes$ne

7. Protein pep$des 9. Pep$des amino acids

Lipid Bile salts Lipases

11. Liver via gall bladder

12. Tongue (lingual)

Stomach Pancreas

Small intes$ne Stomach Stomach Small Intes$ne

Triglyceride (fat) globules emulsied fat droplets

13. Triglyceride monoglyceride and faZy acids

Prac2ce Ques2on 3

3. Describe the control of the secre2on of diges2ve juices in humans in terms of:

a) Nervous control b) Hormonal control

Learning Objec2ves Diges2on & Absorp2on of Macromolecules

Phases of Diges2ve Juice Secre2on

1. Cephalic Neuronal control

2. Gastric Neuronal control Hormonal control

3. Intes2nal Neuronal control Hormonal

Control of Secre2on of Diges2ve Juices Nervous control

Sight, smell, thought or taste of food

Brain

CEPHALIC PHASE

Facial, Glossopharyngeal &

Increased gastric juice secre2on

Stomach

Increased pancrea2c juice

secre2on

Pancreas

Increased saliva

secre2on

Salivary Glands

Vagus Nerves


Distension of gastric walls / Increase in gastric pH

Neurons in the submucosal plexus of stomach

GASTRIC PHASE

Stretch receptors / Chemoreceptors

Increased HCl secre2on

Parietal Cells of Stomach

Increased gastric mo2lity -peristalsis

Smooth Muscle of Stomach

Control of Secre2on of Diges2ve Juices Hormonal control

Distension of gastric walls / Increase in gastric pH

Gastrin

GASTRIC PHASE

Stretch receptors / Chemoreceptors

Stomach

Enteroendocrine cells (G cells) of stomach

Increased gastric juice secre2on

Stomach

LES contract Pyloric sphincter- relax

Sphincters

Be able to describe the role of this hormone in the diges2ve system


Distension of duodenal walls

Sympathe2c Neurons

INTESTINAL PHASE

Stretch receptors

Increased contrac2on delays stomach contents emptying and overload

Pyloric sphincter

Control of Secre2on of Diges2ve Juices Hormonal control

Presence of chyme in the duodenum (amino acids, fapy acids, H+)

Cholecystokinin (CCK) Secre2n

Intes2nal Cells

INTESTINAL PHASE

Increased bicarbonate secre2on

Pancreas

Increased enzyme secre2on

Pancreas

Inhibits gastric juice secre2on

Stomach

Bile ejec2on

Gallbladder

Be able to describe the role of these hormones in the diges2ve system

Summary Cephalic phase (under nervous control): short-lived and

prepares mouth, stomach and small intes2ne for food

Gastric phase: increased gastric juice secre2on, mo2lity (peristalsis) of the stomach and opening of pyloric sphincter. Ini2ated by local nerves and maintained by gastrin hormone

Intes0nal phase promotes diges2on in intes2ne by slowing movement of chyme from the stomach to the small intes2ne (nervous control of pyloric sphincter) to prevent overloading. Meanwhile Secre.n and CCK increase bile, pancrea2c juice secre2on and inhibit gastric juice secre2on

biol 1203 week 2_ls_s15_students (1)

Documents

gastrointes2nal system

circulatory system

accessory diges2ve organs

diges0on breakdown of

digestive system loca2on

large intes2ne defeca2on

buccal cavity anatomy

groups of organs