Question

What is the countercurrent mechanism? Describe the physiological basis of the countercurrent mechanism in the kidney.

Answer 1

Hint: The counter current mechanism operating within the kidney is the major adaptation for the conservation of water. There are two countercurrent processes within the kidneys. They are vasa recta and Henle’s loop.

Complete step-by-step answer:
The Countercurrent mechanism is the special mechanism in our kidney that helps in the production of concentrated urine. The physiological basis for the countercurrent process is a specific arrangement of the loop of Henle and vasa recta. The flow of filtrate in the two limbs of Henle’s loop is in different directions and hence forms a countercurrent. The blood flow through the two limbs of the vasa recta is also in a countercurrent arrangement. The proximity between the vasa recta and Henle’s loop and the countercurrent in them maintains a rising osmolarity towards the internal medullary interstitium, i.e., from\[300mOsmo/L\] in the cortex to around\[1200mOsmo/L\] in the inner medulla. This gradient is caused by urea and \[NaCl\]. \[NaCl\] is transferred by the ascending limb of Henle’s loop that is exchanged with the descending limb of the vasa recta. \[NaCl\] is sent back to the interstitium by the ascending part of the vasa recta. Similarly, lesser amounts of urea enter the thin segment of the ascending limb of Henle’s loop carried back to the interstitium by the collecting tubule.

Note: Unless one is to drink extremely large amounts of water, the urine needs to be excreted in a concentrated way. In a different way, the body will lose much water and the person will suffer from the effects of dehydration and low blood pressure. The process that the kidneys use to concentrate urine is known as the countercurrent mechanism.