Nutrition in Man

1. Nutrition in Man

2. Recap! Crossword puzzle!

3. Lesson Objectives • By the end of the lesson, you should be able to: • State the 3 parts of the small intestine. • Describe the functions of the duodenum in terms of digestion by stating the enzymatic reaction that takes place. • Explain the role of bile in the process of fats digestion in the small intestine.

4. Structure of the small intestine

5. Parts of Small Intestine Three parts: • Duodenum • Jejunum • Ileum

6. Structure 6 metres long!!!

7. Structure Lining of the walls the small intestine contains intestinal glands which secrete digestive enzymes

8. Structure • Walls contain villi and microvilli, and single-cell epithelium, blood and lymph capillaries for absorption of digested food particles

9. Duodenum

10. Duodenum • Structure • Receive pancreatic juice from pancreas via pancreatic duct. • Receive intestinal juice from the intestinal gland • Receive bile(produced from liver, stored in gall bladder and releasedvia bile duct

11. Small intestine (Duodenum) bile bile duct • All three fluids are alkaline • Neutralise the acidic chyme • Provide a suitable alkaline medium (~pH 8.5) for the action of the pancreatic and intestinal enzymes pancreatic juice pancreatic duct intestinal juice

12. Functions Secretion of Intestinal Juice • Functions • Intestinal juice contain digestive enzymes : maltase, protease (erepsin) and lipase

13. Intestine juice • Functions – enzymes

14. DuodenumPancreatic juice • Function Pancreatic juice contain enzymes pancreatic amylase, pancreatic lipase and trypsin

15. Pancreatic juice

16. Bile • Liver cells secrete bile • Alkaline greenish-yellow liquid • Has no enzymesso cannot digest food • Aid in digestion of fats • Bile stored temporarily in gall bladder • When gall bladder contracts, bile flows into duodenum via bile duct

18. Simulate action of Bile • Add a small amount of oil to a beaker of water • Shake it • Add liquid detergent to simulate bile. Observe!

19. big drop of fat • In the small intestine, bile salts emulsify fats. + bile salts Bile salts emulsify fats into tiny fat droplets.

20. big drop of fat • In the small intestine, bile salts emulsify fats. • They lower the surface tension of the fats, that is, they reduce the attractive forces between the fat molecules. + bile salts Bile salts emulsify fats into tiny fat droplets.

21. big drop of fat • In the small intestine, bile salts emulsify fats. • They lower the surface tension of the fats, that is, they reduce the attractive forces between the fat molecules. • This causes the fats to break into tiny fat droplets suspended in water, forming an emulsion. + bile salts tiny fat droplets Bile salts emulsify fats into tiny fat droplets.

22. big drop of fat • In the small intestine, bile salts emulsify fats. • They lower the surface tension of the fats, that is, they reduce the attractive forces between the fat molecules. • This causes the fats to break into tiny fat droplets suspended in water, forming an emulsion. • Note that this is just a physical break-up, but no chemical digestion of fat molecules has occurred. + bile salts tiny fat droplets Bile salts emulsify fats into tiny fat droplets.

23. tiny fat droplets • Emulsification increases the surface area to volume ratio of the fats, speeding up their digestion by lipase. Bile salts emulsify fats into tiny fat droplets.

24. tiny fat droplets • Emulsification increases the surface area to volume ratio of the fats, speeding up their digestion by lipase. + lipase Bile salts emulsify fats into tiny fat droplets.

25. tiny fat droplets • Emulsification increases the surface area to volume ratio of the fats, speeding up their digestion by lipase. • Emulsified fats are digested by lipasesto fatty acids and glycerol. + lipase Bile salts emulsify fats into tiny fat droplets.

26. tiny fat droplets • Emulsification increases the surface area to volume ratio of the fats, speeding up their digestion by lipase. • Emulsified fats are digested by lipasesto fatty acids and glycerol. + lipase fatty acids and glycerol Bile salts emulsify fats into tiny fat droplets.

27. Summary

28. Small intestine Carbohydrate digestion

29. Small intestine Fat digestion • Bile emulsifies fats and breaks them up into minute fat globules • Enlarges surface area of fats • Speed up digestion • End products are fatty acids and glycerol

30. Small intestine Protein digestion • Some digested in the stomach • Undigested proteins enter small intestine • Converted to polypeptides by protease (trypsin)

31. Small intestine

32. Muddiest Point • Any Question?