Question

The loop of Henle is considered an engineering marvel. If the loop were straight, what negative effect would it have on the normal functioning of the kidney? Give your answer with particular relevance to the different permeabilities for water and salt in the various regions of the nephron and how the countercurrent multiplier and countercurrent exchange systems help maintain the osmotic gradient across the cortical medullary axis of the kidneys

Answer 1

The entire countercurrent multiplier system would be non existent

The ascending and descending limb would not be there and countercurrent multiplier effect would also be not there decreasing the concentration of ions and urea in the filtrate and therefore the urea in blood increases

The counter current mechaniem helps to concentrate the filtrate which occurs in loop of henle and vasa recta in medulla region of the kidney

The flow of filtrate in two limbs is in opposite direction and thus forms a counter current

The counter current mechanism helps to maintain a concentration gradient in hlthe medullary interestial fluid which helps in an easy absorption of water from the filtrate present in the collecting duct so that concentration of filtrate is increased in the urine and therefore human urine is always hypertonic that is less of water and more of substrate

With regards to salt,the concentration gradient is mainly caused due to it.Nacl is transported by the ascending limb of loop of henle which is exchanged with descending limb of vasa recta.

Similarly a small amount of urea enters the thin segment of ascending limb which is transported back to interstitial fluid by the collecting duct.