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