A Tour of the Digestive A Tour of the Digestive SystemSystem Mouth

◦ Tongue, teeth, salivary glands, pharynx

◦ Enzymes

Esophagus◦ Epiglottis and choking

◦ Peristalsis

Stomach◦ Cardiac and pyloric sphincters

and stomach cell types

◦ Enzymes and gastric secretions

Pancreas◦ Digestion enzymes, pH

balance and maintenance of blood sugar

Liver / Gall bladder◦ Roles in digestion and

other body processes Small intestine

◦ Specialization – structure and function three sections and of the villi

◦ Enzyme action Large intestine

◦ Functions and anaerobic bacteria within

Rectum and Anus◦ Expulsion of wastes

Small intestine zonesSmall intestine zones3 Zones: Dudodenum, Jejenum, Ilium

• Approx. 6m long

• Most of digestion and absorption of nutrients occur here

Fats break down to Fats break down to molecular level!molecular level!

Glycero

l

Fatty Acid

Fatty Acid

Fatty Acid

Glycerol

Fatty Acid

Fatty Acid

Fatty Acid

Lipase

Fat Fatty Acids and Glycerol

Digestive Enzymes from the Digestive Enzymes from the Interstitial glandsInterstitial glands

Maltase

Maltose (from carbohydrates)Glucose

Peptidase

Peptide (from proteins)Amino Acids

Inside the small intestineInside the small intestineLarge folds

line the intestine called villi and microvilli

= LOTS of surface area

How much? ~600m2 (size of a baseball diamond)

The VilliThe Villi

Outer wall

Inner wall

Pathway for Food

VilliVilliEach villus has a very

thin layer of cells around it (epithelium).

Beneath the cells are a lymphatic vessel and a blood capillary.

Fatty acids and glycerol enter the lymphatic system

Glucose and amino acids enter to the blood system and are taken to the liver where they are processed

A close up look at villiA close up look at villi

Large IntestineLarge IntestineConsists of the colon, the rectum

and the opening at the end, the anus.

Colon has 3 parts◦ascending◦transverse◦descending

How long is it?◦About 1.5m long (about 5 feet)◦Last 20 cm is the rectum

The appendix is a vestigial organ (not needed).

What does the large What does the large intestine do?intestine do?Reapsorption of waterAbsorption of certain vitaminsAlso contains: bile pigments,

heavy metals, and billions of E. coli (providing colour and odour)

What do E. coli do for you?◦break down some indigestible food◦produce some vitamins, amino acids,

and other growth factors

Physical digestion: Teeth and stomach churning broke it into

pieces Bile broke the fats into smaller globs

Chemical digestion: Salivary amylase: starch maltose Pepsin in stomach: protein peptides Pancreatic amylase: starch maltose Trypsin from the pancrea: protein

peptides Lipase from the pancreas: fats glycerol

+ fatty acids

Digestion Summary

Indigestion?Indigestion?Disorders in the large Disorders in the large

intestine and symptomsintestine and symptoms

http://www.youtube.com/watch?v=1ZIK6Ua20JA&feature=channel_page

http://www.youtube.com/watch?v=0yLPtYH6xfE

Overall review of digestion:http://www.youtube.com/watch?v=QtDgQjOGPJM