GI 4: Water & Salt Balance Flashcards
water input to the GI tract is ____L/day
8-10
only ___% of water input is from ingested food/liquid
20
most of the GI water input comes from
secretions
water output of the GI tract ____L/day
0.1
___% of water in the GI tract is reabsorbed
98
most water reabsorption occurs in the ___
small intestine
give 3 reasons why water reabsorption is highest in the small intestine
- increase permeability to H2O
- high osmotic gradient
- high surface area
t/f water is secreted at multiple places in the GI tract
t
in the intestine, water absorption occurs at the ___ and water secretion occurs at the ___ by __cells
vili; crypt (goblet cells)
water only moves by __
osmosis
water follows __
solutes
____ are required for water to move transcellularly
aquaphorin channels
can lactose cross the brush border of the enterocyte?
no, must be digested
what causes diarrhea in lactose intolerance?
lactose can’t be digested to cross the brush barrier, so water moves by osmosis into the lumen of the intestine resulting in loose watery stool
what makes sports drinks popular (in terms of water salt balance)
contain carbs but are hypotonic (unlike juice or soda) so they encourage hydration (water reabsorption into the intestine)
___-g of Na flows through the GI tract by food and secretions each day
25-35
Na has ____directional movement
bi
Na id ___% reabsorbed
90
the highest flux of Na is in the ___
small intestine
the greatest net reabsorption of Na is in the __
colon
what are the 2 route Na can be reabsorbed and are the passive or active?
- paracellular (passive)
2. transcellular (active)
in the small intestine, Na is secreted by ___ and absorbed by ___
crypt cells; vili
in the fed state, what is used as con transport for Na to enter the enterocyte?
amino acids
what is the function of the K/Na ATPase in transcellular movement of Na?
moves Na into the intestine while also keeping its concentration low in the brush border so more Na will enter the apical end by diffusion
Na specific channels are found mostly in the __
colon
what I the effect of aldosterone on Na reabsorption and at the activity of the Na/K pump?
both increased
how does aldosterone promote more Na reabsorption>
increase the making and translocation of Na channels
____ prevent to back flow of Na by the paracellular route in the colon
tight junction
definition of diarrhea
frequent flow of loose, watery stool due to increased motility and or decreased absorption by the intestine
what issues might diarrhea lead to ?
electrolyte imbalance and metabolic acidosis (dehydration)
osmotic diarrhea is caused by ___. Give an example
decreased fluid absorption due to high solute concentration in the lumen (increased osmotic pressure) . Ex: lactose intolerance
secretory diarrhea is caused by ____. Give an example
increased fluid secretion ; active secretion of Cl and Na leading to increased osmotic pressure in the lumen na water following. Ex: cholera
small intestine inflammation involves the destruction of the ___
brush border (loss of vili/microvilli )
what are the 3 things that decrease when the brush border is destroyed in inflammatory diseases?
- brush border enzymes (lactase, kinase, amino peptidases)
- absorption surface area
- absorption and digestion of macronutrients
the destruction of the brush border may lead to ___ diarrhea
osmotic
give 2 examples of inflammatory diseases that destroy the brush border
celiac and chron’s
after an ileal resection, what is an adverse effect?
little to no bile salt reabsorption; little to no bile salt recycling and the liver can’t keep up, leading to decreased bile salt availability
a decrease in bile salt availability may lead to a decrease ___ and __ and an increase in ____ causing ___
fat digestion and fat-soluble vitamin absorption ; cholesterol salt ratio causing gallstones
after ileal resection, there is risk of deficiency of what water-soluble vitamin?
B12
primary lactose intolerance is due to
due to genetics
secondary lactose intolerance is due to
loss of brush border membrane
t/f in Chron’s disease the brush border can be regrown by inflammatory techniques
t
cholera is the infection of the small intestine by ___
V. cholera
the cholera bacteria toxin binds to ___ which keeps the production of ___ active resulting in the ___ of Na and Cl
G protein; cAMP; secretion
cholera results in death in ___% of untreated cases
50
cholera results in massive diarrhea of up to __L/day
20
