1. Human Anatomy and Physiology
Digestion and absorption of nutrients

2. Digestion of carbohydrates
Hydrolysis
Tri- and disaccharides monosaccharides
Monosaccharides
Disaccharide

3. Digestion of carbohydrates
Sources
Sucrose (sugar), lactose (milk), starches (non-animal products)
Fiber not digested by humans
Areas of breakdown
Mouth (salivary amylase)
Duodenum (pancreatic amylase)
Intestine (enterocytes - lactase, sucrase, maltase, a-dextranase)

4. Digestion of carbohydrates

5. Digestion of proteins Proteins peptides amino acids
Stomach Small intestine
Small intestine

6. Digestion of proteins Sources Areas of breakdown
Dietary (plants and animals)
Endogenous (enzymes, hormones, dead cells)
Areas of breakdown
Stomach (pepsin)
Duodenum (pancreatic secretions)
Intestine (enterocytes - peptidases)

7. Digestion of proteins
Stomach
Small intestine

8. Digestion of fats
Triglycerides (neutral fats) fatty acids and 2 monoglycerides
In blood: Triglycerides fatty acids and glycerol

9. Digestion of fats Sources Area of breakdown -emulsion
Dietary - animal and plants
Area of breakdown -emulsion
Mechanical disruption by stomach
Small intestine (bile emulsifies triglycerides, lipase converts them into fatty acid and monoglyceride)
Lecithin prevents reaggregation
Digestion of triglycerides by pancreatic lipase

10. Digestion of fats
Small intestine
Blood

11. Enterohepatic circulation
Bile pathway
Liver, common hepatic duct, gall bladder (storage)
Common bile duct, duodenum, sphincter of Oddi
Absorption (95%), hepatic portal vein, liver
Common Hepatic Duct

12. Fluid absorption
~ 8.2 liters of fluid into the tract (98.5% is absorbed)
Input
Intake 1.5L, salivary gland 1.0L, stomach 1.5L, liver 1.0L, pancreas 1.0L, small intestine 2.0L, colon 0.2L
Absorbed
Small intestine 7.2L, colon 0.85L
Output
Feces 0.15L

13. Absorption Monosaccharides Amino acids
co-transported with sodium by protein transporters
Amino acids
similar mechanism

14. Absorption of lipids Fatty acids and monoglycerides diffuse into cell
Converted to triglyceride
Enter ER and Golgi - chylomicron
Exocytosis into lacteal
Eventually empty into neck veins

15. Absorption in the colon
Proximal
Sodium is actively absorbed
Distal
Secretion of bicarbonate (neutralizes acid from bacterial action)
Absorption of chloride
Resultant gradient allows passive water absorption leading to dry feces

16. Absorption in the colon

17. Disorders of the colon Constipation Diarrhea Decreased colon motility
Colon distention with fiber
Laxatives: decrease water absorption
Diarrhea
Increased colon motility, irritants
Decrease in water absorption, or water secretion into the tract

18. Lactose intolerance
Small intestine