Lecture 20 - colon (freeman) Flashcards Preview

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Flashcards in Lecture 20 - colon (freeman) Deck (12):
1

microbial digestion - perfect environmental conditions

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

2

colon motility

prolonged retention time
propulsion and retropulsion
pacemaker in pelvic flexure

3

neutralization of contents

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

4

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

5

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

6

cecum function

water conservation

7

distal colon function

conserve sodium and water retained earlier for microbial ferementation

8

a high fiber diet will need...

more water for microbial fermentation/buffering

9

ion transport: Na absorption in proximal colon

electoneutral exchange with H

10

ion transport: Na absorption in distal colon

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

11

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

12

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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