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Digestion and Metabolism

Terms

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What are the constituents of saliva?
Amylase, Electrolytes, IgA, Mucus, Lyzosyme, lots of h20
what are the tissue layers of the digestive tract?
Mucosa-secren of mucus, enzy, hormones
submucosa-blood and lymph
muscular externa-segmentation and peristalsis
serosa- protective outer layer connective tissue.
how is the digestive tract regulated?
neural control- enteric and normal.
Hormones
Paracrine secrn.
how does swallowing occur?
Muscular contractions co-ordinated by swallowing centre in medulla and pons.
Stomach
Mechanically breaks up, begins chemical digestion of protein and fat.
Does not absorb anything much.(aspirin/some lipid sol drugs)
Where does HCL come from? and what does it do?
HCL produced by parietal cells, (also produce intrinsic factor) it activates pepsinogen and lingual lipase, helps break down food, destroys bacteria and pathogens
Gastric motility
food stretches tummmy and it relaxes to hold more. Rhythum of peristalsis controlled by pacemaker cells in longitudinal musc layer. At pyloric region, squirted in small amounts regularly into duodenum.
Regulation of gastric secretion, what are the phases?
1 Cephalic: sight smell food, excites vagus nerve, Incr secrn and motility.
2 Gastric:stomach distention, food chemicals via vagus nerve& Gastrin release(chems).
3.Intestinal:presence of acid and part digestd food via intestinal gastrin release.
how are the secrn stopped?
the secretions are stopped via enterogastric reflexes, release of secretin, cholycystokinin, gastric inhibitory peptide which all stop secretion.
what does the liver do?
it makes bile, which goes to the gall bladder, then thru bile duct, joining up with panreatic duct forming hepatopancreatic ampulla, emptying into duodenum. reg by sphincter of Oddi.
Pancreas
the pancreas secrets about 1500 ml pancreatic juice into the duodenum. it secretes zymogens activated once in duodenum.
cholecystokinin
stimulates gall bladder to expel bile, relaxes sphicter of oddi.
Secretin
inhibits gastric galnd secrn increases output of pancreatic juice.
intestinal motility
Chyme mixes with intestinal juice, bile and pancreatic juice, chyme churned to incr SA, chyme moves towards large intestine by segmentation and peristalsis.
Absorption
nucleases hydrolise nucleic acids. vitamins absorbed unchanged. minerals absorbed all alonng sm intestine. most h20 abs via large intestines.

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