Water & Electrolyte Movement In The GI Tract

Question 1

What is the most abundant substance in chyme?

Answer 1

Water

Question 2

What happens in the small intestine?

Answer 2

Water reabsorption

Question 3

What % of water is reabsorbed in small intestine?

Answer 3

80%

Question 4

How much ingested & secreted water enters small intestine per day & how much passes into large intestine?

Answer 4

8000ml - small intestine

1500ml - large intestine

Question 5

Which part of the gut reabsorbs most water?

Answer 5

Jejunum

Question 6

Where does water reabsorption happen?

Answer 6

Small intestine

Question 7

Is water reabsorbed in the stomach and how much?

Answer 7

Yes abundantly small amounts

Question 8

Why are small amounts of water reabsorbed in the stomach?

Answer 8

Has a much smaller SA available for diffusion and lacks the solute-absorbing mechanisms that create the osmotic gradient necessary for absorbing water

Question 9

How much fluid is reabsorbed? (%)

Answer 9

98%

Question 10

What happens to the 2% of fluid and how many ml is that?

Answer 10

200ml being excreted in stools

Question 11

Describe the epithelial membranes of the small intestine in terms of water

Answer 11

They are very permeable to water & net water diffusion occurs across the epithelium whenever a water concentration difference is established by the active absorption of solutes

Question 12

What accounts for the most actively transported solutes?

Answer 12

Na+

Question 13

Why does Na+ account for the most actively transported solutes?

Answer 13

Because it constitutes the most abundant solute in chyme- it is actively transported from the lumen in the cell membranes of the ileum & jejunum

Question 14

What is luminal membrane transport variably coupled with?

Answer 14

Glucose, amino acids or other substances

Question 15

The contents of the colon are….

Answer 15

Iso-osmotic

Question 16

What does iso-osmotic in the colon mean?

Answer 16

Conc in lumen of colon = that of blood

Question 17

What ions are reabsorbed in the colon?

Answer 17

K+ and Cl-

Question 18

What happens in k+ reabsorption in the colon?

Answer 18

In general, K+ reabsorption is by passive diffusion

The net movement begin determined by the potential difference between the lumen and intestinal capillaries

Question 19

What can diarrhea result in to do with k+?

Answer 19

Severe hypokalaemia (loss of K+)

Question 20

What happens in Cl- reabsorption in the colon?

Answer 20

It is actively reabsorbed in exchange for bicarbonate resulting in intestinal contents becoming more alkaline