Wat is Counter Current Mechanism?????
Higher vertebrates have evolved a counter current mechanism to create hypertonic urine for conserving body water, so necessary for land life.
Henle’s loop and capillary loop play an important role in this mechanism. Glomerular fluid in the Henle’s loop and the blood in the vasa recta flow in opposite directions in the two descending limb and toward the renal cortex in the ascending limb. These two counter current systems help in concentrating urine by maintaining high salt concentration around the nephrons and collecting ducts.
Kidneys also play a role in osmoregulation, i.e., maintenance of water and Na+ contents of blood. This is achieved by countercurrent mechanism in the loop of Henle and by the action of antidiuretic hormone from posterior pituitary gland of brain and another hormone aldosterone from the adrenal gland.