Question

how does the loop of henle create a concentration gradient in the mammalian kidney?

Answer 1

Answer:

Nephron is the structural and functional units of kidney. Their function is to help in the process of urine formation.

A nephron is divided into two parts;

Renal corpuscle and a renal tubule

Renal corpuscle is further having two divisions; Glomerulus and the Bowman’s capsule

Renal tubule is having the components; Proximal convoluted tubule (PCT), Loop of Henle (LH- descending and ascending limb), and the Distal convoluted tubule (DCT).

Function of Glomerulus: It is a tuft/dense network of capillaries which brings in the blood toward the nephron for urine formation

Bowman’s capsule: It is a sac like structure which provides support to the glomerulus and helps to conduct the filtrate from the renal corpuscle to the renal tubule

Renal tubular segments:

Proximal convoluted tubule (PCT): maximum reabsorption of the filtrate takes place in the PCT. value being nearly 65%. For that reason PCT is known to have numerous mitochondria.

Loop of Henle: It plays a very important role in concentrating the urine. It happens by the process of counter current mechanism. For this process, the loop of Henle remains in close proximity with the blood vessels called as vasa recta.

The loop of Henle is divided into two parts; the descending limb of loop of Henle and the ascending limb of loop of Henle.

The loop of Henle enters into the medullary region of the kidney which has a high osmolarity; a high amount of the solute, the value being around 1200 milliosmol per liter.

Due to this high osmolarity within the medullary region, the amount of the solvent is very less. For that reason; from the descending limb of loop of Henle a significant amount of water gets returned back to the body thereby concentrating the urine.

Also furthermore, the ascending limb of loop of Henle is impermeable to the solvent however is permeable to the solutes. Therefore thus from the ascending limb of loop of Henle; a significant amount of solutes including urea, and NaCl are made to return back to the body through the blood vessels; vasa recta. This thus helps to restore and maintain the solute as well as solvent concentration of the body. Also this adds on to the increase in the osmolarity of the medullary region of the kidneys.

This complete process is called as counter current mechanism and it plays a very important role in concentrating the urine.

Distal convoluted tubule (DCT): The distal convoluted tubule is further involved in the reabsorption of water and solutes.

Thus in the different segments of the nephron the urine gets concentrated thereby restoring the solute and solvent concentrations of the body.