1. The Small Intestine -major site of digestion and absorption -Diameter= 2.5cm, Length= 6-7m

2. Components of the Small Intestine Duodenum –first 25-30cm most of digestion occurs here enzymes from pancreas and bile from gall bladder enter to digest: –lipids, carbohydrates, proteins

4. Sodium Bicarbonate in the Duodenum The enzymes in the duodenum require a basic pH=9.0 to function. Stomach acid has a pH=2.0. Sodium bicarbonate from the pancreas alters the pH to accommodate these enzymes. http://www.execulink.com/~ekimmel/secretin_0.htm

5. Jejunum –digestion and absorption Ileum –absorption –moves undigested material into large intestine

6. Cross Section of Small Intestine

8. Structure related to Function Circular Folds, Villi and Microvilli –all increase SA to maximize absorption of nutrients Length –increases time available for nutrient absorption Capillary Beds –absorb nutrients and transport to body cells Lacteals –absorb lipids into lymphatic system

9. The Large Intestine (Colon) D = 7.6 cm, L = 1.5 m –reabsorbs water, salt, minerals it takes 5.6 L of water to digest our food each day, Why? 1. Dissolve digestive enzymes 2. Lubricate food material 3. Dissolve nutrients to allow absorption

10. The Large Intestine (Colon) all but 0.2 L is reabsorbed in the large intestine feces (undigested food material) are usually very solid, low water content

12. The Large Intestine

13. Bacteria in the large intestine

14. bacteria can’t survive in the harsh environments of the stomach and small intestine –the damp colon is a good breeding ground some are useful, produce vitamins B12, K some are harmful, e. coli

16. Escherchia coli

17. Where does E.coli come from? -present in the feces of most mammals -most strains are harmless

18. How does E.coli get into lakes? -runoff waters after heavy rains -sewage contamination

19. What are the symptoms of an E.coli infection?

20. E. Coli Infection Causes severe diarrhea, How? –peristalsis speeds up –not enough time for water re-absorption to occur Treatment? –drink lots of fluids –antibiotics prescribed