Question

A. Describe the histological process by which the kidney concentrates urine, name the cells and tissues involved?

B. How may the kidneys change if they become diseased?

Answer 1

Kidneys concentrate the urine by 2 mechanism-

1. Counter current mechanism

2. By secreting ADH.

KIDNEY has some unique mechanism called counter current mechanism which is responsible for development of medullary gradient and hyper osmolarity of interstitial fluid in inner medulla.

The direction of flow of fluid in two limbs of Loop of Henle are opposite to each other. Also, the flow of blood in Vasa recta is also opposite to flow of fluid in Loop of Henle. This difference on flow in these two vessels makes a counter current mechanism.

Sodium and chloride are actively reabsorbed from ascending limb of henle and transferred to descending limb.

This cycle continue and and concentration of urine increases.

Also, sodium chloride reabsorbed from ascending limb of henle enters the medullary interstitium. From here, it enters the descending limb of Vasa recta. Simultaneously water diffuses from descending limb of Vasa recta into medullary interstitium.

2. Final concentration of urine is achieved by ADH action. ADH cause reabsorption of water DCT and collecting tubule. This concentrate the urine.

B. If kidney become diseased, then the structure of kidney will be destroyed. The nephrons,which are the functional unit of kidney will not work. This will lead stoppage of working of kidney's function of excretion.

this will cause renal failure.