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28 Cards in this Set

  • Front
  • Back
how much fluid is secreted into the GI tract each day? reabsorbed by SI?
- 9L of fluid secreted

- SI reabsorbs 8L

- LI reabsorbs 90% of last liter
what are the different GI spinchters?
1) UES
2) LES
3) pyloric
4) oddi
5) ileocecal
6) internal anal
7) external anal
how does the pyloric sphincter work? ileocecal?
- 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
what is the signaling in the GI tract with the plexuses?
- information goes from submucosal plexus --> myenteric plexus to change muscle tone
what do circular & longitudinal muscles do to the GI tract?
- circular does mixing

- longitudinal gives you peristalsis
what are the 3 big salivary glands?
- parotid, submaxillary, sublingual
what are the 8 major functions of saliva?
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
what does the saliva look like in the gland vs in the duct? what special cells does it have to help it contract?
- 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
why do you hypersalivate before you throw up?
- to get more bicarb to buffer the mouth
why does the secretion become hypo-osmotic in the duct?
- because sodium & chloride are being removed & bicarb & K are being pumped in less

- 1 bicarb exchanged for 1 chloride
what happens with the different concentrations of the ions because of the flow rates?
- 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
how do Ach & NE work on the saliva receptors?
- Ach increases IP3 & Ca2+

- NE works through increased cAMP
what is the source, target & action of gastrin:
- source: antrum of stomach

- target: parietal cells in stomach

- action: increase H+ secretion
what is the source, target & action of CCK:
- source: duodenum & jejunum

- target: pancreas & gallbladder

- action: increase enzyme secretion & increase contraction
what is the source, target & action of secretin:
- source: duodenum

- target: pancreatic & bile ducts

- action: increase bicarb secretion
what is the source, target & action of gastrin releasing peptide:
- source: vagal nerve endings

- target: antrum of stomach

- action: increase gastrin release
what is the source, target & action of somatostatin:
- source: stomach & duodenum

- target: stomach, pancreas, liver

- action: decrease gastrin, decrease endocrine & exocrine secretions, decrease bile flow
what is the source, target & action of gastric inhibitory peptide:
- source: duodenum & jejunum

- target: pancreas

- action: decrease fluid absorption
what is the only neuroendocrine molecule of the GI system?
- GRP released from vagal nerve endings
what is the main breakdown of the stomach?
- protein

- acid can activate protein-digesting enzyme (pepsin) & acid also denatures protein

- mucus protects stomach from digesting itself
what is the resevoir function of stomach? how small does it want to get food ideally?
- compliance allows increase in volume with little increase in pressure

- wants to get food <1mm diameter
where is intrinsic factor secreted and absorbed?
- secreted in stomach, binds to B12 & absorbed in the terminal ileum
what are the 3 agonists of parietal cells and what do they do?
- 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
how does the stomach make H to be secreted into the lumen? what does this mean for the pH of the capillaries near stomach?
- 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
how does the antrum signal to the fundus?
- 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)
how does the enzyme activation of the pancreas occur?
- trypsinogen released & turned into trypsin by enterokinase

- then goes & converts rest of the enzymes
what are the inactive precursors released by pancreas? active?
- inactive: trypsinogen, chymotrypsinogen, proelastase, procarboxypeptidase A & B

- active: lipase & amylase
how are salivary secretions unique in their nervous system control?
- they are essentially controlled by the nervous system (autonomic) without a hormonal regulatory component