Countercurrent flow in gas exchange
A) is when water and circulatory fluid flow in opposite directions across the respiratory surface.
B) is not found in invertebrates.
C) is a less-efficient mechanism than co-current flow.
D) decreases the efficiency of gas exchange when compared with water flowing in the same direction.
E) results in water leaving the gills with a high partial pressure of oxygen.

Question

Quizplus · Accepted Answer

Countercurrent flow is a mechanism where water and blood flow in opposite directions across the respiratory surface, maximizing the gradient for gas exchange and increasing efficiency.

Countercurrent Flow in Gas Exchange