1. GUT PHYSIOLOGY Absorption 2 Dr. Jack Grider Rm 12-004 Sanger Hall
2009

2. Digestion &Absorption: Lipids
Problem: lipids are hydrophobic and enzymes are hydrophillic
Solution: Bile (bile salts)

3. Digestion &Absorption: composition of bile
Water & solutes
Solutes (4% in hepatic and 10% in gallbladder)
60% bile acids
15% phospholipid
15% electrolyte (Na+, K+, Cl-, HCO3-)
7% cholesterol
2% bilirubin
1% protein

4. Digestion &Absorption: Lipids

5. Digestion &Absorption: Lipids

6. Digestion &Absorption: Lipids
? Potential role as a signaling molecule?

7. Digestion &Absorption: Lipids
Bile Acid = Cholic Acid
Conjugated Bile Acid=Taurocholic acid
Conjugated Bile Salt=Sodium Taurocholic acid

8. Digestion &Absorption: Lipids
Hydrophillic
side
Hydrophobic
side

9. Digestion &Absorption: Lipids
Micelle increases solubility of FA by >1000 fold

10. Digestion &Absorption: Lipids
Oral cavity: lingual lipase
Stomach: gastric lipase; emulsification
Intestine: lipase, colipase, bile salts

11. Digestion &Absorption: Lipids

12. Digestion &Absorption: Lipids

13. Digestion &Absorption: Water & Electrolyte

14. Digestion &Absorption: Water & Electrolyte

15. Digestion &Absorption: Water & Electrolyte
Potassium
passive absorption in small intestine
secretion in colon if <25mM in lumen
absorption in colon if >25 mM in lumen

16. Digestion &Absorption: Water & Electrolyte
Chloride & bicarbonate
Bicarbonate secretion in duodenum
Absorption of both in jejunum
Chloride absorption and bicarbonate secretion in ileum and colon.

17. Digestion &Absorption: Water & Electrolyte
Calcium
brush border protein carrier
cytosolic calcium binding protein (calbindin)
basolateral active transport into capillaries
Regulation by PTH and Vitamin D

18. Digestion &Absorption: Water & Electrolyte
Iron
dietary is Fe3+ (ferric) but absorbed as soluble Fe2+ (ferrous) form
pH-dependent conversion (acidic optimum)
Protein complexed absorbed by endocytosis.
epithelial cell storage as complex with apoferritin to form ferritin
binds to blood protein transferrin
mucosal block & desquamation

19. Digestion &Absorption: Vitamins
multiple pathways for water -soluble ones: both passive and specialized mechanisms.
fat soluble absorbed with micell.

20. Digestion &Absorption: Vitamins