In the countercurrent exchange system of fish gills,
A) blood and water flow in the same direction.
B) blood and water flow in opposite directions.
C) blood and water are separated by a thick polysaccharide barrier.
D) blood flow in the gills reverses direction with every heartbeat.

Question

Quizplus · Accepted Answer

In the countercurrent exchange system of fish gills, blood and water flow in opposite directions. This helps maximize the exchange of oxygen and carbon dioxide between the two fluids. As water flows over the gills, it becomes increasingly oxygen-depleted, while blood flowing through the gills becomes increasingly oxygen-rich. This gradient allows for efficient diffusion of oxygen from water to blood, and carbon dioxide from blood to water.

In the Countercurrent Exchange System of Fish Gills