Question

Which of the following factors is responsible for the formation of concentrated urine?

• A. Hydrostatic pressure during glomerular filtration
• B. Low levels of antidiuretic hormone
• C. Maintaining hyperosmolarity towards the medullary interstitium in the kidneys
• D. Secretion of erythropoietin by juxtaglomerular complex

Answer 1

The correct option is C Maintaining hyperosmolarity towards the medullary interstitium in the kidneys

Urine formation takes place in the kidneys. The nephrons are the basic filtration units of the kidney.

Henle’s loop is a hairpin shape structure in the nephrons. The special arrangement of Henle’s loop and vasa recta (network of capillaries) along with the counter-current mechanism helps in maintaining and increasing the osmolarity towards the inner medullary interstitium in the kidneys. This interstitial gradient helps in concentrating the urine.

Hence, option c is correct.

The hydrostatic pressure in the glomerular capillaries facilitates the filtration of blood during urine formation but does not contribute to the formation of concentrated urine.

Hence, option a is incorrect.

Antidiuretic hormone (ADH) helps in the reabsorption of water from the glomerular filtrate and contributes in making the urine concentrated. But low levels of ADH will make the urine dilute.

Hence, option b is incorrect.

Erythropoietin helps in the formation of RBCs.

Hence option d is incorrect.