Lecture 20 - colon (freeman) Flashcards Preview

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Flashcards in Lecture 20 - colon (freeman) Deck (12):

microbial digestion - perfect environmental conditions

availability of substrate
prolonged rentention time
anaerobic conditions
continuous buffering
hydration of contents


colon motility

prolonged retention time
propulsion and retropulsion
pacemaker in pelvic flexure


neutralization of contents

high Cl and low bicarb concentration in pancreatic fluid and intestinal fluid


how are contents neutralized in ileum and distal jejunum?

Cl/HCOe exchange

Cl may provide a source for exhange of bicarb for neutrailization later in the cecum


large intestine function

absorb large volumes of water, Na and bicarb in response to a cyclic pattern of microbial digestion

95% of Na, bicarb and water in large intestine is reabsorbed daily


cecum function

water conservation


distal colon function

conserve sodium and water retained earlier for microbial ferementation


a high fiber diet will need...

more water for microbial fermentation/buffering


ion transport: Na absorption in proximal colon

electoneutral exchange with H


ion transport: Na absorption in distal colon

aldosterone-controlled (Na/K exchange - Na out, K in)


enterosystemic cycle

a process that conserves water lost in digestive secretions

important when:
1. feeding practices alter "normal grazing" patterns (like horses being fed twice a day)
2. animals with diarrhea


horses and enterosystemic cycle

horses are continuous grazers and consume hi fiber diets - large ECF volumes are drawn into colon daily and need to be replaced.

horses fed in ways that deviate from normal grazing --> plasma volume can decrease by 15%! --> result: hypovolemia (shock)

decrease in ECF --> hypovolemia --> activates renin-angiotensin-aldosterone system --> Increase renin --> increase angiotensin --> increase aldosterone --> aldosertone secretion can increase colonic and kidney reabsorption of Na and water --> dehydrating components to point of impaction and colic!

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