Assume the following values for osmolarity at 3 particular l

Assume the following values for osmolarity at 3 particular locations in the kidney: 1) 50 mOsM for the tubular fluid at the distal end of the distal tubule, 2) 300 mOsM for the interstitial fluid in the renal cortex, 3) 1500 mOsM for the interstitial fluid in the inner medulla of the kidney. Which one of the following best approximates the osmolarity of the urine that would be produced in the absence of antidiuretic hormone?

a) 50 mOsM

b) less than 50 mOsM

c) 1500 mOsM

d) 175 mOsM

e) 900 mOsM

Solution

Answer

Osmolarity: The concentration of solution in terms of the solute particles present per liter of the solution.

As the reabsorption of water occurs in the nephrons of kidney, concentration of fluid increases in the nephron. Thus, its osmolarity will be high.

This reabsorption of water takes place by the antidiuretic hormone(ADH). In the absence of ADH, the collecting ducts does not reabsorb water. As a result, the osmolarity of the fluid that enters the renal pelvis will be diluted with water and decreases to 50mOsm/L which is 1200-1400mOsm/L in general.

Therefore, option A is correct.