Download - The Small Intestine and Large Intestine
The Small Intestine and The Small Intestine and Large IntestineLarge Intestine
Review
Salivary Juice contains:1. Water2. Salivary amylase
Gastric Juice contains:1. Mucous2. HCl3. Pepsinogen
The Small IntestineAverages about 6 metres in length
Small diameter
Why is the small intestine so long? Time and surface area for digestion to occur
The first 25 cm is called the duodenumduodenumDucts from the gallbladder (bile) and
pancreas (pancreatic juice) enter the duodenum
Bile
BileBile: Emulsifies fat into droplets that disperse in water
Pancreatic Juice
1. Water2. Sodium bicarbonate3. Lipase4. Trypsin5. Nuclease6. Pancreatic Amylase
Pancreatic Juice Source of Enzymes Pancreas Lipids Glycerol + fatty acids(fat droplets) Lipase
Nucleic acids Nucleotides nuclease Source of enzyme – also Sm. Intestine
Optimal pH: 8
Pancreatic Juice
Source of Enzymes Pancreas Starch maltose pancreatic amylase
Protein shorter polypeptides Trypsin
Optimal pH: 8
Question
What is the optimal pH of the small intestine and how is it achieved?
Optimal pH is 8The bile and pancreatic juice neutralizes
the pH of the chyme (stomach pH 2)
Question
It has been suggested that the surface area of small intestines is analogous to the surface area of a tennis court. How?
A: The wall of the small intestine contains finger-like projections called villi (sing. villus)villi (sing. villus)
Villi Villi i increase the surface area of the intestinal wall which increases the amount of nutrients that can be absorbed.
Villi
A villus has an outer layer of epithelial cells that contain thousands of tiny extensions called microvillimicrovilli Forms a brush border
where intestinal enzymes are secreted
Greatly increase the surface area available for nutrient absorption
Villi
A villus contains blood capillaries and a small lymphatic capillary called a lacteallacteal
Glucose and amino acids enter the Glucose and amino acids enter the blood capillaries of a villusblood capillaries of a villus Hepatic portal vein Hepatic portal vein liver liver
Glycerol and fatty acids are packages Glycerol and fatty acids are packages as lipoproteins and enter the lactealas lipoproteins and enter the lacteal Lymphatic systemLymphatic system After absorption, they are carried to the After absorption, they are carried to the
cells by the bloodstreamcells by the bloodstream
Small Intestine
Absorption occurs across the wall of each villi and continues until the nutrients are absorbed
This occurs actively (with ATP) or passively (without ATP)
Anatomy of the Small Intestine
Interstitial glands
Walls of the duodenum and small intestine are lined with millions of interstitial glands Produce Interstitial juice which contains Peptidases Maltase Sucrase Lactase
Interstitial juice finishes the digestion of protein and starch
Interstitial JuiceSource of enzymes – interstitial gland /small intestine
Peptides Amino acid peptidase
Maltose Glucose + Glucose (dissacharide) maltase (monosacharide)
Optimal pH: 8
Interstitial JuiceSource of enzymes – interstitial gland /small
intestine
Sucrose Glucose + Fructose(disaccharide) sucrase (monosaccharide)
Lactose Glucose + Galactose(disaccharide) lactase (monosaccharide)
Optimal pH: 8
The Large Intestine
Consists of the cecumcecum, the coloncolon, the rectumrectum and the anal canalanal canal
Larger in diameter than small intestine But shorter (1.5 meters)
Does not produce digestive enzymes, but does absorb water, salts and some vitamins
Also stores indigestible waste until defecation
The Cecum
Lies below the junction of the small intestine
Has a small projection called the appendixappendix
What is the role of the appendix?
A: Plays a role in fighting off infections in humans.
The Colon
Includes the ascending colonascending colon (right side), transverse colontransverse colon (passes abdominal
cavity), descending colondescending colon (left side) sigmoid colonsigmoid colon (enters the rectum)
Does not play a role in nutrient absorption Absorbs water from waste before it is
eliminated
The Rectum
The last 20 cm of the large intestine
Opens at the anus, where defecation of indigestible material is expelled
Main function is storage of feces
Components of feces: 3/4 water 1/4 solid
Question
Why is feces so smelly?A: The rectum contains bacteria that act on indigestible material resulting in an unpleasant odour and also produce gas, which has a foul smell.
Intestinal Bacteria
99% of colon bacteria are obligate anaerobes (poisoned by oxygen)
Break down indigestible material and produce vitamins that our bodies need
Perform services for us!
Question
What are two common disorders that are related to the large intestine?
A: Diarrhea and constipation
Diarrhea Prolonged diarrhea can lead to dehydration due
to water loss and disturb heart contractions due to ion imbalance
2 major causes of diarrhea: 1. Infection of the lower intestinal tract
Food poisoning from contaminated foodIrritated intestinal wallIncrease in peristalsis
2. Nervous stimulationStimulation of intestinal wall
Constipation Feces are dry and hard and
defecation does not occur regularly
To prevent constipation: Diet rich in water and fibre Take laxatives
Prevent water from being absorbed and expel the contents of the colon
Chronic constipation due to hemorrhoids, which are large, inflamed blood vessels of the anus
Photo References
http://healthy-diet.maxupdates.tv/the-basics-of-the-human-digestive-system/
http://www.cancer.umn.edu/cancerinfo/NCI/CDR350260.html http://cureibszone.com/diarrhea http://remedynatural-herbs.com/home-remedies-for-constipation http://www.thenibble.com/reviews/news/2007-01.asp http://www.nlm.nih.gov/medlineplus/ency/imagepages/1128.htm http://www.smithinst.ac.uk/Projects/PG2004/CASE-Unilever04/
ProjectSummary http://blog.beliefnet.com/chatteringmind/
2006_07_01_chatteringmind_archive.html http://www.coloniccleansing.org/ http://www.nlm.nih.gov/medlineplus/ency/imagepages/9390.htm