NEET PG Medical – 2018 – Question – 18
Components responsible for counter current mechanism in kidney are all except:
a) Sodium outflow in thick ascending limb
b) Water outflow in thin descending limb
c) Sodium outflow in thin ascending limb
d) Flow of tubular fluid from PCT to DCT
Show Answer
Correct Answer – C
Answer: C. Sodium outflow in thin ascending limb
Counter-current system occurs in kidney
A system in which inflow runs parallel to, counter to, and in close proximity to the outflow for some distance.
2 countercurrent mechanisms available:
- Countercurrent multiplier at Loop of Henle
- Generate high medullary osmotic gradient pressure
- Countercurrent exchanger at vasa recta of medullary capillaries
- Helps in maintain the medullary osmotic pressure gradient
Substances involved in countercurrent mechanism include: - Sodium actively absorbed with co-transport of potassium & chlorine in thick ascending limb of loop of Henle.
- Water reabsorbed in thin descending limb of loop of Henle.
- Urea diffuse out from the medullary collecting ducts into medullary interstitium.
