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Small Intestine

10 ft. length, 1 inch diameter, large surface area, majority of absoption


10 inches


3 feet


6 feet, ends at ileocecal valve


Function of --- and microvilli
Increase the surface area for absorption; brush border enzymes found on the surfaces of microvilli participate in chemical breakdown of carbohydrates and proteins; cell division within intestinal glands produces new cells that move up

salivary amylase

Digestion of carbohydrates: mouth:---

mechanical breakdown

digestion of carbohydrates: stomach: ---

pancreatic amylase

digestion of carbohydrates: duodenum: ---


absorption of ---
Absorption into epithelial cells: glucose and galactose - sodium symporter (secondary active transport); fructose - facilitated diffusion
Movement out of epithelial cell into bloodstream - by facilitated diffusion


Digestion of ---:
stomach - HCl denatures or unfolds proteins, pepsin turns proteins into peptides (smaller AA chains)

pancreatic enzymes

small intestine: --- split peptide bonds between different amino acids


brush border enzymes --- split amino acids at amino end of molecule


splits dipeptides

amino acids and dipeptides

absorption of --- & ---
Absorption into epithelial cells of duodenum and jejunum - active transport with Na+ or H+ ions (symporters)
Movement out of epithelial cell into blood - diffusion

lingual lipase

Digestion of lipids mouth: ---

gastric lipase

Digestion of lipids stomach: --- important in infants

pancreatic lipase

Digestion of lipids small intestine
emulsification by bile from liver to form micelles
--- splits triglycerides into fatty acids and monoglyceride
no lipase enzymes in the brush border

Fat soluble vitamins

Absorption of lipids
- small fatty acids enter absorptive cells & then blood by simple diffusion
- larger lipids are sequestered within micelles after emulsification by bile; lipids enter cells by simple diffusion leaving bile salts behind in gut
-bile salts reabsorbed into blood & reformed into bile in the liver
---- (A K D E) are able to enter cells with the lipids


Absorption of Lipids
-Inside epithelial cells are fats and rebuilt and coated with protein to form ---
--- leave intestinal cells by exocytosis into a lacteal - travel in lymphatic system to reach subclavian veins -removed from the blood by the liver and fat tissue


Absorption of ---
sources: GI secretions, ingested foods and liquids
Enter epithelial cells by diffusion and secondary active transport
- sodium and potassium move by active transport
-chloride, iodide and nitrate follow passively
-iron, magnesium and phosphate ions use active transport
Intestinal Ca++ absorption requires vitamin D and parathyroid hormone


Absorption of ---
Fat-soluble ---
travel in micelles and are absorbed by simple diffusion with lipids
-water soluble --- absorbed by diffusion
B12 must combine with intrinsic factor from the stomach partietal cells before it is transported into the cells of the ileum - absorbed by receptor mediated endocytosis


Absorption of ---
9L fluid enter GI tract per day
Small intestine absorbs 8L
Large intestine absorbs 90% of last liter
Absorption is by osmosis through cell walls into vascular capillaries inside villi

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