Countercurrent exchange is evident in the flow of ________.
A) water across the gills of a fish and the blood within those gills
B) blood in the dorsal vessel of an insect and that of air within its tracheae
C) air within the primary bronchi of a human and the blood within the pulmonary veins
D) water across the skin of a frog and the blood flow within the ventricle of its heart

Question

Quizplus · Accepted Answer

Countercurrent exchange is a mechanism where substances flow in opposite directions in parallel tubes, maximizing the exchange of substances between them. This is seen in the flow of water across the gills of a fish and the blood within those gills, where oxygen diffuses from the water into the blood, while carbon dioxide diffuses from the blood into the water. The opposite flow of substances maximizes the exchange of oxygen and carbon dioxide between the water and the blood.

Countercurrent Exchange Is Evident in the Flow of ________