Question

In the lungs of birds, where does gas exchange occur?

A. Across thin parenchymal cells in the alveoli
B. In the alveolar sacs
C. Across a thin network of bronchioles and blood vessels
D. Inside of the air sacs

Answer 1

a) across thing parenchyma cells in the alveoli


Gas exchange occurs only in alveoli. Alveoli are made of thin-walled parenchymal cells, typically one-cell thick, that look like tiny bubbles within the sacs. Alveoli are in direct contact with capillaries (one-cell thick) of the circulatory system.