Final answer:
The osmolarity in the interstitial fluid increases as you move from the outer to the inner cortex of the kidney.
Step-by-step explanation:
The osmolarity in the interstitial fluid increases as you move from the outer to the inner cortex of the kidney.
As shown in the diagram of the countercurrent exchange mechanism within the loop of Henle, the osmolarity of the filtrate increases as it descends into the renal medulla. This is due to the water flowing from the filtrate to the interstitial fluid, causing an increase in osmolality.
Thus, the osmolarity of the interstitial fluid would be higher in the inner cortex of the kidney compared to the outer cortex.