Question

What is the osmolarity (in mOsmol $L^{–1}$) in the outer cortex and inner medulla region?

• A.
  300 and 900 respectively
• B.
  600 and 300 respectively
• C.
  1200 and 300 respectively
• D.
  300 and 1200 respectively

Answer 1

The correct option is D

300 and 1200 respectively
Henle's loop is a U-shaped that plays a significant role in maintaining high osmolarity of cortex and medullary interstitial fluid. The osmolarity increases from 300 mOsmolL-1 in the cortex to 1200 mOsmolL-1 in the inner medulla by counter current mechanism. It helps in maintaining the concentration gradient, which in turn helps in easy movement of water from collecting tubules.