Refer to the figure. Where would you most likely find this pattern of blood and water flow?

Question

Refer to the figure.  Where would you most likely find this pattern of blood and water flow?

Quizplus · Accepted Answer

This pattern of blood and water flow is most likely found in a fish gill. The figure shows a countercurrent exchange system, which is a mechanism used by fish to efficiently extract oxygen from water. The blood flows in the opposite direction to the water, maximizing the gradient of oxygen concentration between the two, and allowing the fish to obtain a greater amount of oxygen from water than would be possible with a concurrent flow system.

Refer to the Figure