L2: Water absorption And Secretion In The Gastrointestinal Tract

Question 1

Where does the absorption of non electrolyte nutrients occur?

Answer 1

The small intestine

Question 2

Diarrhoea is caused by ___ or ___

Answer 2

Lack of absorption or excess secretion

Question 3

Absorption of water occurs via ___

Answer 3

Osmosis

Question 4

Large net water absorption occurs in the ___

Answer 4

Jejunum

Question 5

Solvent drag is responsible for what?

Answer 5

Considerable Na and urea absorption in the jejunum

Question 6

What is the predominant mode of absorption?

Answer 6

Paracellular transport

Question 7

What absorption pathway is dominant in leaky epithelia?

Proximal renal tubule, small intestine

Answer 7

Paracellular transport

Question 8

What absorption pathway is dominant in tight epithelia?

Renal collecting duct, urinary bladder

Answer 8

Transcellular pathway

Question 9

All transcellular Na absorption involves what pump?

Answer 9

Na/K ATPase at basolateral membrane

Question 10

Movement of Na via the apical surface is mediated by what four channels/transporters?

Answer 10

• Na/glucose or Na/Amino Acid cotransporters
• Na/H Exchanger
• parallel Na/H and Cl/HCO3 exchangers
• epithelial Na channel

Question 11

What happens if Na/K ATPase doesn’t work?

Answer 11

• electrochemical gradient isn’t maintained(sodium build up inside cell)
• glucose and proteins not moved into cell

Question 12

Osmotic diarrhoea is due to a disturbance in ___

Answer 12

Absorption

Question 13

Secretory diarrhoea is due to a disturbance in ___

Answer 13

Secretion

Question 14

What is the physiology behind cholera?

Answer 14

• cholera toxin activates adenylate cyclase
• causes elevation of cAMP
• this opens Cl channel in apical membrane of crypt epithelial cells
• causes prolonged secretion of Cl, Na and water