Vasa recta is a ' ' shaped blood capillary that helps in maintaining the osmolarity gradient in the medullary interstitium. and its proximity with the Loop of Henle is responsible for the Counter current mechanism. Antidiuretic hormone (ADH) or vasopressin increases the reabsorption of water in the distal convoluted tubule, collecting tubules and collecting ducts of the nephrons in the kidneys. As a result, the reabsorption of water from the glomerular filtrate is increased making urine more concentrated.