205textnotes46

205textnotes46 - + + HCO 3-) - Cl-passing via C1 channels...

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Fat digestion is assisted by bile (Figure 21-23) which coats globules of lipid, thereby allowing the fat to form an emulsion within the gastric juices. Bile causes the production of small lipid droplets which increases the surface availability of the fat for digestive enzymes to work. These enzymes include lipases and phospholipases (Figure 21-8). Digestion --------------------------------------------------------- C. Regulation of GI Function: --------------------------------------------------------- Stomach digestion of protein (15-20%) - protein load = dietary intake and cellular debris - very acidic environment in stomach - parietal cells stimulated by gastrin increase their secretion of H + from parietal cells. - H + s are secreted into lumen via H + -K + ATPase pump (Figure 21-14) (H 2 0 + CO 2 <= Carbonic Anhydrase => H 2 CO 3 <==> H
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Unformatted text preview: + + HCO 3-) - Cl-passing via C1 channels into lumen 1 ) before protein enters stomach, relatively high [H+] 2) when protein enters, it binds with H+ and decreases [H+] 3) decreased [H + ] -&gt; stimulates increased gastrin -&gt; stimulates parietal cells to increase [H + ] - parasympathetic nervous system also stimulates parietal cells - caffeine can also stimulate parietal cells (leads to stomach ulcers) - inhibiting parietal cells by CCK and secretin (later) -pepsinogen + H +-&gt; pepsin (enzyme) - pepsin begins chemical digestion of protein - pepsin inactivated at pH &gt; 5 - peristalsis in stomach achieves mixing and hence some mechanical digestion. - greatest force of contraction provided by the antrum - digestion of carbohydrate via salivary amylase stops due to stomach acidity Gastric Emptying...
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