Intestinal Fluid and Electrolytes Flashcards
How much fluid comes into the GI tract in food?
2.0 L
How much fluid is secreted into the GI tract per day?
6.5 L
How much fluid is reabsorbed from the GI tract per day?
6.5 L
Has a large surface area (villi) and functions mostly in electrolyte and nutrient absorption
Small intestine
In the small intestine, there is no secretion of
K+
Has a small surface area with no villi and functions in electrolyte and water reabsorption
Large intestine
Secreted into the large intestine via aldosterone
K+
There is no nutrient absorption in the
Large intestine
During a meal, the villous epithelial cells in the small\ intestine are responsible for absorbing most of the
Na+
Are absorbed passively in the villi of the small intestine
Cl- and K+
The primary mechanism of NaCl absorption during the interdigestive period
Parallel Na-H and Cl-HCO3 exchange
The villous epithelial cells in the ileum and the surface epithelial cells in the colon are responsible for absorbing most of the
NaCl
This occurs via an
Electroneutral mechanism
Here carbonic anhydrase (CA) generates intracellular carbonic acid, which splits into H+ and HCO3- and drives the
Exchange process
Electroneutral NaCl absorption is inhibited by intracellular increases in
cAMP, cGMP, and Ca2+
Electrogenic Na+ absorption occurs in the
Small intestine
Increase Na+ absoprtion in the colon as they do in the collecting duct
Mineralocorticoids (aldosterone)
Occurs in the crypts of both the small and large intestine
Electrogenic Cl- secretion
This chloride is secreted through
CFTR
Believed to occur mainly in the crypts rather than in either the epithelial cells of the villus or surface cells of the colon
Cl- secretion
Normal basal Cl- secretion is low and insignificant compared to
Cl- absorption
Bacterial toxins and hormones can act on
Cl- secretion/absorption
What are the two major types of diarrhea?
- ) Osmotic
2. ) Secretory
A nonabsorbable substance draws water and electrolytes into the gut lumen in
Osmotic diarrhea
An example of osmotic diarrhea is
Lactose intolerance
Electrolytes and fluid are actively secreted into the gut in
Secretory diarrhea
A classic cause of secretory diarrhea is
Cholera
Traveler’s Diarrhea is due to E. coli enterotoxigenic strains carrying a toxin related to
Cholera Toxin
Electrogenic Na+ absorption occurs in the large intestine and enhanced by
Aldosterone
Occurs mainly in the crypts rather on the surface epithelium
Cl- secretion
In osmotic diarrhea, a non absorbable substance like lactose draws water and electrolytes into the
Gut lumen
In secretory diarrhea, electrolytes and fluid are actively secreted into the gut due to a
Toxin
