Vasa recta blood osmolality is critical to maintaining the countercurrent mechanisms of the nephron. where is vasa recta blood osmolality the highest?

The vasa recta blood osmolality filtrates the highest at the tip of the loop of Henle.

Vasa recta refers to the straight arterioles of the kidney. It is the capillaries paralleling the loop of Henle. In the vasa recta, the blood is carried at a very slow rate. It is critical in maintaining the countercurrent exchange to prevent the washout of concentration gradients.

Idont really understand