Physiology- Loop of Henle

Question 1

what does LoH do?

Answer 1

counter current multiplier, increases gradient

Question 2

describe roles of ascending and descending limb

Answer 2

ascending

• actively co-transports Na+ & Cl- ions out of the tubule lumen into the interstitium
• impermeable to H20

descending

• freely permeable to H2O but relatively impermeable to NaCl

Question 3

what is the overall effect?

Answer 3

• Concentrates fluid on the way down & promptly re-dilutes it on the way back up (by removing NaCl)
• Fluid which enters the distal tubule is more dilute than plasma (hyposmotic)

Question 4

what is the site of water regulation?

Answer 4

collecting duct - permeability under influence of ADH

• this relies on creation of a hyperosmotic medullary interstitium