GI 4: Water & Salt Balance

Question 1

water input to the GI tract is ____L/day

Answer 1

8-10

Question 2

only ___% of water input is from ingested food/liquid

Answer 2

20

Question 3

most of the GI water input comes from

Answer 3

secretions

Question 4

water output of the GI tract ____L/day

Answer 4

0.1

Question 5

___% of water in the GI tract is reabsorbed

Answer 5

98

Question 6

most water reabsorption occurs in the ___

Answer 6

small intestine

Question 7

give 3 reasons why water reabsorption is highest in the small intestine

Answer 7

1. increase permeability to H2O
2. high osmotic gradient
3. high surface area

Question 8

t/f water is secreted at multiple places in the GI tract

Answer 8

t

Question 9

in the intestine, water absorption occurs at the ___ and water secretion occurs at the ___ by __cells

Answer 9

vili; crypt (goblet cells)

Question 10

water only moves by __

Answer 10

osmosis

Question 11

water follows __

Answer 11

solutes

Question 12

____ are required for water to move transcellularly

Answer 12

aquaphorin channels

Question 13

can lactose cross the brush border of the enterocyte?

Answer 13

no, must be digested

Question 14

what causes diarrhea in lactose intolerance?

Answer 14

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

Question 15

what makes sports drinks popular (in terms of water salt balance)

Answer 15

contain carbs but are hypotonic (unlike juice or soda) so they encourage hydration (water reabsorption into the intestine)

Question 16

___-g of Na flows through the GI tract by food and secretions each day

Answer 16

25-35

Question 17

Na has ____directional movement

Answer 17

bi

Question 18

Na id ___% reabsorbed

Answer 18

90

Question 19

the highest flux of Na is in the ___

Answer 19

small intestine

Question 20

the greatest net reabsorption of Na is in the __

Answer 20

colon

Question 21

what are the 2 route Na can be reabsorbed and are the passive or active?

Answer 21

1. paracellular (passive)

2. transcellular (active)

Question 22

in the small intestine, Na is secreted by ___ and absorbed by ___

Answer 22

crypt cells; vili

Question 23

in the fed state, what is used as con transport for Na to enter the enterocyte?

Answer 23

amino acids

Question 24

what is the function of the K/Na ATPase in transcellular movement of Na?

Answer 24

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

Question 25

Na specific channels are found mostly in the __

Answer 25

colon

Question 26

what I the effect of aldosterone on Na reabsorption and at the activity of the Na/K pump?

Answer 26

both increased

Question 27

how does aldosterone promote more Na reabsorption>

Answer 27

increase the making and translocation of Na channels

Question 28

____ prevent to back flow of Na by the paracellular route in the colon

Answer 28

tight junction

Question 29

definition of diarrhea

Answer 29

frequent flow of loose, watery stool due to increased motility and or decreased absorption by the intestine

Question 30

what issues might diarrhea lead to ?

Answer 30

electrolyte imbalance and metabolic acidosis (dehydration)

Question 31

osmotic diarrhea is caused by ___. Give an example

Answer 31

decreased fluid absorption due to high solute concentration in the lumen (increased osmotic pressure) . Ex: lactose intolerance

Question 32

secretory diarrhea is caused by ____. Give an example

Answer 32

increased fluid secretion ; active secretion of Cl and Na leading to increased osmotic pressure in the lumen na water following. Ex: cholera

Question 33

small intestine inflammation involves the destruction of the ___

Answer 33

brush border (loss of vili/microvilli )

Question 34

what are the 3 things that decrease when the brush border is destroyed in inflammatory diseases?

Answer 34

1. brush border enzymes (lactase, kinase, amino peptidases)
2. absorption surface area
3. absorption and digestion of macronutrients

Question 35

the destruction of the brush border may lead to ___ diarrhea

Answer 35

osmotic

Question 36

give 2 examples of inflammatory diseases that destroy the brush border

Answer 36

celiac and chron’s

Question 37

after an ileal resection, what is an adverse effect?

Answer 37

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

Question 38

a decrease in bile salt availability may lead to a decrease ___ and __ and an increase in ____ causing ___

Answer 38

fat digestion and fat-soluble vitamin absorption ; cholesterol salt ratio causing gallstones

Question 39

after ileal resection, there is risk of deficiency of what water-soluble vitamin?

Answer 39

B12

Question 40

primary lactose intolerance is due to

Answer 40

due to genetics

Question 41

secondary lactose intolerance is due to

Answer 41

loss of brush border membrane

Question 42

t/f in Chron’s disease the brush border can be regrown by inflammatory techniques

Answer 42

t

Question 43

cholera is the infection of the small intestine by ___

Answer 43

V. cholera

Question 44

the cholera bacteria toxin binds to ___ which keeps the production of ___ active resulting in the ___ of Na and Cl

Answer 44

G protein; cAMP; secretion

Question 45

cholera results in death in ___% of untreated cases

Answer 45

50

Question 46

cholera results in massive diarrhea of up to __L/day

Answer 46

20