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28 Cards in this Set
- Front
- Back
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how much fluid is secreted into the GI tract each day? reabsorbed by SI?
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- 9L of fluid secreted
- SI reabsorbs 8L - LI reabsorbs 90% of last liter |
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what are the different GI spinchters?
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1) UES
2) LES 3) pyloric 4) oddi 5) ileocecal 6) internal anal 7) external anal |
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how does the pyloric sphincter work? ileocecal?
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- tells everything to slow down when there is stretch
- ileocecal: stretch to relax & allow stuff to go through & when there is stretch on other side it constricts |
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what is the signaling in the GI tract with the plexuses?
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- information goes from submucosal plexus --> myenteric plexus to change muscle tone
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what do circular & longitudinal muscles do to the GI tract?
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- circular does mixing
- longitudinal gives you peristalsis |
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what are the 3 big salivary glands?
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- parotid, submaxillary, sublingual
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what are the 8 major functions of saliva?
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1) mucin moistens oral mucosa
2) moistens dry food & cools hot food 3) dissolves food for taste buds 4) buffers oral cavity with bicarb 5) alpha-amylase & lipase (only function at neutral pH) 6) lysozyme to control bacterial flora 7) mineralization of teeth 8) protective pellicle on teeth |
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what does the saliva look like in the gland vs in the duct? what special cells does it have to help it contract?
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- in the gland it is isotonic to the blood
- in the duct bicarb is secreted into it, sodium out, chloride out, K+ in --> becomes hypoosmotic - myoepithelial cells |
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why do you hypersalivate before you throw up?
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- to get more bicarb to buffer the mouth
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why does the secretion become hypo-osmotic in the duct?
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- because sodium & chloride are being removed & bicarb & K are being pumped in less
- 1 bicarb exchanged for 1 chloride |
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what happens with the different concentrations of the ions because of the flow rates?
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- sodium osmolarity increases because it overwhelms the system
- bicarb levels off & chloride gets higher not because of chloride bicarb exchanger but because more chloride channels are opening up |
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how do Ach & NE work on the saliva receptors?
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- Ach increases IP3 & Ca2+
- NE works through increased cAMP |
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what is the source, target & action of gastrin:
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- source: antrum of stomach
- target: parietal cells in stomach - action: increase H+ secretion |
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what is the source, target & action of CCK:
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- source: duodenum & jejunum
- target: pancreas & gallbladder - action: increase enzyme secretion & increase contraction |
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what is the source, target & action of secretin:
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- source: duodenum
- target: pancreatic & bile ducts - action: increase bicarb secretion |
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what is the source, target & action of gastrin releasing peptide:
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- source: vagal nerve endings
- target: antrum of stomach - action: increase gastrin release |
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what is the source, target & action of somatostatin:
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- source: stomach & duodenum
- target: stomach, pancreas, liver - action: decrease gastrin, decrease endocrine & exocrine secretions, decrease bile flow |
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what is the source, target & action of gastric inhibitory peptide:
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- source: duodenum & jejunum
- target: pancreas - action: decrease fluid absorption |
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what is the only neuroendocrine molecule of the GI system?
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- GRP released from vagal nerve endings
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what is the main breakdown of the stomach?
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- protein
- acid can activate protein-digesting enzyme (pepsin) & acid also denatures protein - mucus protects stomach from digesting itself |
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what is the resevoir function of stomach? how small does it want to get food ideally?
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- compliance allows increase in volume with little increase in pressure
- wants to get food <1mm diameter |
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where is intrinsic factor secreted and absorbed?
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- secreted in stomach, binds to B12 & absorbed in the terminal ileum
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what are the 3 agonists of parietal cells and what do they do?
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- 3 agonists: CCK (Ca), H2 (cAMP), Ach (Ca)
- vesicles containing hydrogen pumps fuse & they are put into the membrane - when not needed anymore pulled back into vesicles |
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how does the stomach make H to be secreted into the lumen? what does this mean for the pH of the capillaries near stomach?
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- via dissociation of CO2 + H20 via carbonic anhydrase
- H pumped into lumen, bicarb pumped into blood - pH of the blood capillaries near stomach become a little alkaline |
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how does the antrum signal to the fundus?
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- low pH stimulates D cells --> SST is released which is neg regulated of G cells --> not secreting gastrin
- when pH is raised gastrin is released from antrum --> effects chief cells to release pepsinogen & parietal cells to release H+ & also enterocoffin cells (ECL) to release histamine (positive regulator of chief cells) |
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how does the enzyme activation of the pancreas occur?
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- trypsinogen released & turned into trypsin by enterokinase
- then goes & converts rest of the enzymes |
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what are the inactive precursors released by pancreas? active?
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- inactive: trypsinogen, chymotrypsinogen, proelastase, procarboxypeptidase A & B
- active: lipase & amylase |
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how are salivary secretions unique in their nervous system control?
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- they are essentially controlled by the nervous system (autonomic) without a hormonal regulatory component
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