Digestion, Absorption and Transport

1. Digestion, Absorptionand Transport Copyright 2005 Wadsworth Group, a division of Thomson Learning

2. Digestion and Absorption • Digestion • Process by which large molecules are mechanically and chemically broken down into smaller particles • Absorption • Process by which nutrients are absorbed by the gastrointestinal (GI) tract and enter the body for use

3. GI Tract • Also called Alimentary Canal • Long muscular tube • Controlled by hormone and hormone like substances

4. Types of Digestion • Mechanical • Mixing, chewing, and muscular mastication of food • Chemical • When enzymes and chemical secretions are added to food to finalize the breakdown

5. Copyright 2005 Wadsworth Group, a division of Thomson Learning

6. Digestion • Mouth • Tongue • Teeth • Mastication Copyright 2005 Wadsworth Group, a division of Thomson Learning

7. Digestion • Pharynx • Epiglottis • Esophagus • Esophageal sphincters • Bolus Copyright 2005 Wadsworth Group, a division of Thomson Learning

8. Digestion • Stomach • Chyme • Pyloric sphincter Copyright 2005 Wadsworth Group, a division of Thomson Learning

9. Digestion • Small intestine • Duodenum • Jejunum • Ileum Copyright 2005 Wadsworth Group, a division of Thomson Learning

10. Digestion • Large intestine = colon • Ileocecal valve • Appendix • Rectum • Anus Copyright 2005 Wadsworth Group, a division of Thomson Learning

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12. Digestion • Accessory Organs – contribute to the digestive process, but are not part of the digestive tube • Pancreas • Liver • Gallbladder Copyright 2005 Wadsworth Group, a division of Thomson Learning

13. Muscular Action of Digestion • The muscles of the digestive tract keep things moving at the right pace • Slow enough to get the job done and fast enough to make progress Copyright 2005 Wadsworth Group, a division of Thomson Learning

14. Stomach Muscles Circular Longitudinal Diagonal – stomach Copyright 2005 Wadsworth Group, a division of Thomson Learning

15. Muscular Action of Digestion • Peristalsis – wavelike muscular contractions that move food through the GI tract • Stomach about 3 waves per minute • Sm I about 1 wave every 4-5 seconds Copyright 2005 Wadsworth Group, a division of Thomson Learning

16. Peristalsis Copyright 2005 Wadsworth Group, a division of Thomson Learning

17. Muscular Action of Digestion • Segmentation – contracting of circular muscles where no forward of backward motion occurs Copyright 2005 Wadsworth Group, a division of Thomson Learning

18. Muscular Action of Digestion • Segmentation Copyright 2005 Wadsworth Group, a division of Thomson Learning

19. Muscular Action of Digestion • Sphincters – a circular muscle surrounding and able to close, a body opening • Esophageal • Pyloric • Ileocecal • Anal Copyright 2005 Wadsworth Group, a division of Thomson Learning

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21. Secretions of Digestion • Enzyme – a protein that facilitates a chemical reaction (making or breaking bonds) • Catalyst • Made of protein • Facilitate hydrolysis – adding water • Specific – work on single substrate Copyright 2005 Wadsworth Group, a division of Thomson Learning

22. Secretions of Digestion • Saliva • Salivary glands • Water, salts, mucus, enzymes Copyright 2005 Wadsworth Group, a division of Thomson Learning

23. Secretions of Digestion • Stomach • Gastric glands • Gastric juice • Water, enzymes, hydrochloric acid (HCl) • Mucus Copyright 2005 Wadsworth Group, a division of Thomson Learning

24. Secretions of Digestion • Pancreas • Pancreatic juice • Enzymes, bicarbonate Copyright 2005 Wadsworth Group, a division of Thomson Learning

25. Secretions of Digestion • Liver • Bile • Emulsifier • Gallbladder Copyright 2005 Wadsworth Group, a division of Thomson Learning

26. Secretions of Digestion • Protective factors • Bacteria • Biotin • Folate • Vitamin B6 • Vitamin B12 • Vitamin K Copyright 2005 Wadsworth Group, a division of Thomson Learning

27. The Final Stage • Colon • Fermentation of undigested residues • Stools Copyright 2005 Wadsworth Group, a division of Thomson Learning

28. Absorption • Absorption – process by which nutrients are absorbed by the GI tract and enter the body for use Copyright 2005 Wadsworth Group, a division of Thomson Learning

29. Absorption Copyright 2005 Wadsworth Group, a division of Thomson Learning

30. Absorption in theSmall Intestine • Most absorption (95%) occurs in the small intestine (duodenum) absorptive structures • Villi • Microvilli • Crypts Copyright 2005 Wadsworth Group, a division of Thomson Learning

31. The Small Intestinal Villi Copyright 2005 Wadsworth Group, a division of Thomson Learning

32. The Small Intestinal Villi Copyright 2005 Wadsworth Group, a division of Thomson Learning

33. Blood – portal circulation – to liver for processing Water soluble nutrients Protein Carbohydrates Vitamins – B vitamins and Lymphatic – lymphatic circulation Fat soluble nutrients Fats Vitamins – A, D, E, K Absorption- Two Pathways

34. Lymphatic System • Loosely organized system of vessels and ducts that convey fluids toward the heart • Lymph – a clear yellowish fluid that is almost identical to blood except that it contains no red blood cells or platelets. Transports fat soluble substrates Copyright 2005 Wadsworth Group, a division of Thomson Learning

35. Regulation of Digestion and Absorption • Homeostasis – balance; things don’t change • Factors affecting GI function • Physical immaturity • Aging • Illness • Nutrition Copyright 2005 Wadsworth Group, a division of Thomson Learning

36. Regulation of Digestion and Absorption • Controlled by two systems • Hormonal/endocrine • Nervous system Copyright 2005 Wadsworth Group, a division of Thomson Learning

37. Feedback mechanisms • Self regulation • pH level • Pyloric sphincter • Presence of acid in small intestine • Pancreatic enzymes