Question

What are air sacs ? Why are they surrounded by blood vessels ?

Answer 1

Answer:

Air sacs are found as tiny sacs off the larger breathing tubes (tracheae) of insects, as extensions of the lungs in birds, and as end organs in the lungs of certain other vertebrates. They serve to increase respiratory efficiency by providing a large surface area for gas exchange.

Each air sac is surrounded by a network of fine blood vessels (capillaries). The oxygen in inhaled air passes across the thin lining of the air sacs and into the blood vessels. ... When oxygen passes into the bloodstream, carbon dioxide leaves it. Carbon dioxide (CO2) is a waste product of cellular metabolism...