Salt and water balance

Question 1

What are the parts of the colon

Answer 1

The ascending, transverse, descending, sigmoid and rectum

Question 2

What is the surface of the epithelium in the colon like

Answer 2

Smooth with no villi

Contains crypts deep into epithelium acting as capillaries to suck water out.

Many mucus secreting cells to ease passge of faeces

Question 3

Why are crypts useful in water reabsorption

Answer 3

They cause a capillary suction pressure

Question 4

Where is the greatest amount of water reabsorbed in the GIT

Answer 4

Small intestine - jejunum

Question 5

How is sodium reabsorbed in the proximal bowel

Answer 5

Na:H+ exchange or AA-cotransport

Question 6

How is sodium reabsorbed in the jejunum

Answer 6

Na:Glc cotransport or Na:Cl- cotransport

Question 7

How is sodium reabsorbed in the colon

Answer 7

Na+ channel

Question 8

How are Cl- ions reabsorbed in the colon

Answer 8

Cl-:HCO3- exchange

Question 9

What causes congenital chloride diarrhea

Answer 9

Cl-/HCO3- exchange lacking in ileum

Question 10

How does the cholera toxin cause diarrhea

Answer 10

Permanently activated adenylyl cyclase, elevating cAMP in the crypt cells, releasing lots of Cl-