1. Exercise 39A
Digestive Physiology

2. The Digestive Process Ingestion Propulsion Mechanical Digestion
Chemical Digestion
Absorption
Defecation

3. Motility vs. Mixing
The difference between peristalsis and segmentation:
Peristalsis moves food along the tract. Segmentation is mixing and part of the mechanical digestion process.

4. Absorption of Nutrients
Nearly all occurs in the small intestine.
80% of the electrolytes and virtually all food
Most nutrients are absorbed by active transport.
Glucose, amino acids, & nucleic acids are absorbed by secondary active transport with sodium.
Iron and calcium require transport proteins (ferritin) or cofactors (vitamin D).
Anions follow Na+.
Vitamins -
Fat soluble (A, D, E & K) vitamins are carried with micelles. Much of the K is absorbed in the colon.
Water soluble vitamins diffuse with the exception of B12, which requires intrinsic factor.

5. Hormonal regulation of bile release

6. Exocrine tissues of the pancreas

7. Activation of pancreatic proteases in the duodenum

8. Regulatory mechanisms for release of pancreatic juice

9. Chemical Digestion
Carbohydrates & proteins

10. Chemical Digestion
Lipids & Nucleic acids

11. Protein digestion in the small intestine

12. Bile salts emulsify fats

13. Absorption of lipid
Dietary fats are absorbed into the “lacteals” of the lymphatic system before being transferred to the circulatory system.

14. Lacteals

15. The End