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22 terms

Digestion Lecture 28

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Small Intestine
10 ft. length, 1 inch diameter, large surface area, majority of absoption
duodenum
10 inches
jejunum
3 feet
ileum
6 feet, ends at ileocecal valve
Villi
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: ---
monosaccharides
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
Proteins
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
aminopeptidase
brush border enzymes --- split amino acids at amino end of molecule
dipeptidase
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
Chylomicrons
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
electrolytes
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
Vitamins
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
Water
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