A Tour of the Digestive System 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 zones 3 Zones: Dudodenum, Jejenum, Ilium Approx. 6m long Most of digestion and absorption of nutrients occur here

Fats break down to molecular level! Glycerol Fatty Acid Glycerol Fatty Acid Lipase Fat Fatty Acids and Glycerol

Digestive Enzymes from the Interstitial glands Maltase Maltose (from carbohydrates) Glucose Peptidase Peptide (from proteins) Amino Acids

Inside the small intestine Large folds line the intestine called villi and microvilli = LOTS of surface area How much? ~600 m 2 (size of a baseball diamond)

The Villi Outer wall Inner wall Pathway for Food

Villi Each 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 villi

Large Intestine Consists 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 intestine do? Reapsorption of water Absorption of certain vitamins Also 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? Disorders in the large intestine and symptoms Overall review of digestion: