1. Digestion and Absorption

2. Digestive System Reduces particle size
Helps to absorb micronutrients and trace elements
Sets a physical and immunologic barrier

3. Digestion
Breaks down
Carbohydrates (starch and sugar) → single sugar molecules
Proteins → amino acids
Fats → fatty acids, glycerol

4. Enzymes
Proteins that break bonds

5. The Digestive System
Is a long tube from the mouth to the anus

6. Peristalsis
Muscular contractions that move food along throughout Digestive System

7. The Esophagus Long tube Connects pharynx to the stomach
Peristalsis, muscle contraction
Lower esophageal sphincter
Heartburn

8. The Stomach
Lower esophageal sphincter controls entry and exit from stomach
Storage capacity of ~4 cups
Secretion of hydrochloric acid, and enzymes
Stomach secretes about ml of gastric juice daily
pH of stomach is low, 1 to 4; kills many bacteria and micro-organisms
Formation of chyme

9. Stomach Acid Activates digestive enzymes
Partially digests dietary protein
Assists in calcium absorption
Makes dietary minerals soluble for absorption

10. The Small Intestine Folded walls with villi projections
Absorptive cells are located on the villi
Increases intestinal surface area 600x
Rapid cell turnover
About 5-7 meters
Most digestion and absorption happens here

11. Nutrient Absorption
Passive diffusion: driven by concentration; fats, water, some minerals
Active absorption: uses energy; glucose and amino acids

12. Absorption Digestion → small particles End products of digestion:
Carbohydrates → monosaccharides
Proteins → amino acids
Fats → glycerol, fatty acids

13. Absorption Through small intestine walls Absorbed into
Blood – water soluble nutrients
Lymph – fat soluble nutrients
Blood → liver → general circulation
Liver detoxifies and repackages

14. Summary of Fat Absorption

15. The Gradual Breakdown of Large Starch Molecules

16. The Large Intestine ~3 1/2 feet in length No villi or enzymes present
Little digestion occurs
Absorption of water, some minerals, vitamins
Bacteria break down fiber; produce Vitamin K
Formation of feces for elimination

17. Rectum Stool remains Stimulates elimination Muscle contraction
Anal sphincters
Voluntary control
Opens for elimination

18. Salivary Glands
Saliva
Works in mouth
Moistens
Digests starch

19. The Pancreas Produces glucagon and insulin (endocrine)
Manufactures digestive enzymes→ small intestine
Secretes pancreatic juices
Bicarbonate needed to neutralize chyme when it enters small intestine

20. The Gallbladder Stores bile Concentrates it
Releases to small intestine when needed

21. Digestion in the Stomach
Different nutrients leave the stomach at different rates:
—Carbohydrates first, followed by protein, fat, and fibrous foods

22. Features of Digestion and Absorption
92% to 97% of the diet is absorbed
Small intestine—key role in digestion and absorption
Intestines: 7 meters long
—Villi and microvilli/brush border

23. Lipids
The major portion of fat digestion takes place in the small intestine

24. Large Intestine 5 feet long
Bacterial action to produce gases and organic acids
Some vitamins formed here