Lecture 17 - SI secretion (Freeman) Flashcards Preview

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Flashcards in Lecture 17 - SI secretion (Freeman) Deck (15):
1

brunners glands

protects duodenal wall from digestion

2

crypts

pits which secrete almost pure ECF (Cl-) into lumen via cystic fibrosis transmembrane regulator (CFTR) which are immediatley absorbed by thte villi

3

crypt epithelium

= secretory

4

villous epithelium

= absorptive

5

what does cAMP do to the neutral absorptive processes in villus tip cells?

blocks them and stimulates Cl- secretion by crypt cells

6

what does activation of Cl- secretory process in the crypt by enterotoxins cause?

Na movement into lumen thru paracellular route, which causes net secretion of salt and water into intestinal lumen.

therefore secretion is enhanced and absorption is blocked and excessive fluid ends up in the lumen = diarrhea

7

what is a common way to treat diarrhea

the substrate-coupled Na absorptive processes in villi are unaffected. so if glucose is added to an oral electrolyte solution it will enhance water and sodium absorption thru the substrate-coupled Na transporter

8

secretory diarrhea and extracellular space

- net secretion and failed absorption (from enterotoxin) --> diarrhea --> fluid lost from ECS and cant be absorbed from lumen --> depletion of ECS and cause death from dehydration and electrolyte imbalance

9

treatment for secretory diarrhea and extracellular space

glucose (salt pump is not functioning, but the substrate-coupled Na pump is!)

10

systems that control intestinal secretion

neural control
endocrine control
agents that INCREASE NET SECRETION
immune system

11

neutral control

adrenergic stimulation enhances absorption

cholinergic stimulation enhances secretion

12

endocrine control

glucocorticoids increase Na absorption in SI and colon

mineralcorticoids increase Na absorption in colon ONLY

13

agents that INCREASE NET SECRETION

GI transmitters: VIP, prostaglandins, and serotinin

they block coupled salt absorption on the villus and induce Cl secretion in the crypts much as enterotoxins

14

immune system

inflammatory cells can help activate events that will increase secretion of Cl (similar to some enterotoxins)

**E.coli does NOT damage cell - ENTEROTOXIN does**

15

cystic fibrosis

important example on how secretion of Cl- plays a role in digestion

- most common fatal genetic disease
- body's exocrine glands secrete an abnormally thick sticky mucus
cause: no channel to secrete Cl- (and therefore salt and water)
effects: plugs lumen and breathing

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