Lec36

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Lec36

  1. 1. Digestion and Absorption of Fats<br />Agitation in the stomach breaks the large drops of fats into small drops and disperses them throughout the chyme, this process called emulsification<br />Most of the emulsification occurs in the duodenum under influence of bile<br />Bile salts and lecithin are important for emulsification of fat<br />The structure of bile salt and lecithin consist of hydrophobic in one side and hydrophilic on the other side<br />
  2. 2. Digestion and Absorption of Fats<br />Pancreatic lipase breaks down triglycerides to monoglyceride and free fatty acids<br />Another function of bile salts and lecithin is to surround fatty acid and monoglyceride to form micelles<br />The bile salt micelles also acts as transport medium to carry monoglyceride and free fatty acids to brush borders<br />Monoglyceride and free fatty acids are absorbed into the blood but the bile salts released back to the chyme <br />
  3. 3. Digestion and Absorption of Fats<br />Triglycerides are reassemble inside the cells and packaged into chylomicrons <br />Chylomicrons are composed of 90% triglyceride, 5% cholesterol, 4% phospholipid, 1% protein.<br />Chylomicrons leave the cells and enter lymph vessels called Lacteals<br />Short and medium chain fatty acids are absorbed by simple diffusion and can directly enter capillary<br />
  4. 4. Digestion and Absorption of Fats<br />Fat Bile + Agitation Emulsified Fat<br />Emulsified Fat Pancreatic lipase Fatty acid &<br /> 2 monoglyceride<br />
  5. 5. Transport of Lipids Across Intestinal Epithelium<br />
  6. 6. Fatty Acid Absorption<br />
  7. 7. Water and Na absorption<br />Most of the water and Na enters the GI tract are absorbed in the small intestine<br />The brush border is permeable to both water and Na ion<br />Na and water absorbed by transcellular transport through intestinal epithelial cells or by paracellular transport through tight junction<br />At the basal and lateral membranes of the cells, Na ions are transported into extracellular fluid of tissue and blood vessels<br />This causes osmosis of water<br />
  8. 8. Aldosterone enhances Na absorption<br />During dehydration, large amount of aldosterone secreted<br />Aldosterone causes increased Na absorption by intestinal epithelium and this in turn causes increases in absorption of Cl ions and water <br />The function of aldosterone in the intestinal tract is the same as that of aldosterone in the renal tubules<br />
  9. 9. Absorption of Chloride <br />Chloride absorbed by diffusion in the upper part of the small intestine<br />Transport of chloride ions follow the sodium ions<br />
  10. 10. Absorption of Bicarbonate in the Small Intestine<br />When Na ions are absorbed, moderate amount of hydrogen ions are secreted into the lumen of the gut<br />Hydrogen ions combine with bicarbonate ions to form carbonic acid<br />Carbonic acid dissociate to form water and carbon dioxide<br />Carbon dioxide absorbed into the blood and expired through the lungs<br />
  11. 11. Absorption of Iron<br />Iron absorbed in the small intestine<br />Iron combines with blood plasma to form transferrin and can be released to tissue cells<br />In the cell, iron combines with protein apoferritin to form ferritin<br />The iron stored as ferritin is called storage iron<br />Total body iron is regulated mainly by altering the rate of absorption<br />
  12. 12. Absorption in the Large Intestine<br />Cells and secretions of the large intestine have no digestive functions<br />Resident bacteria break down some of the indigestible carbohydrate and use released nutrients <br />These bacteria synthesize some B complex vitamin and vitamin K that are absorbed<br />The colon absorbs small amounts of salts and water<br />

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