Blood Flow Through the Gills of an Elasmobranch is Arranged

Question

Blood flow through the gills of an elasmobranch is arranged in a __________ fashion.
A)countercurrent
B)concurrent
C)crosscurrent
D)convection

Accepted Answer

Countercurrent flow allows for efficient oxygen uptake from the water as it flows over the gill lamellae. Water and blood flow in opposite directions, which maintains a concentration gradient for oxygen uptake across the entire length of the gill filament. This maximizes the exchange of gases, ensuring that the oxygen uptake is highly efficient.