In birds, where does oxygen go after it is inhaled?

In birds, the inhaled oxygen first travels to the air sacs, which serve as an essential part of their unique respiratory system. Birds have a highly specialized and efficient respiratory structure that includes not only lungs but also a series of air sacs. When a bird inhales, the oxygen-rich air fills the air sacs rather than just entering the lungs.

This adaptation allows for a continuous flow of air through the lungs, ensuring that the oxygen is effectively exchanged with carbon dioxide during both inhalation and exhalation. The air sacs act as bellows, aiding in the movement of air in a unidirectional pattern through the lungs, which enhances the efficiency of gas exchange.

This system provides birds with a steady supply of fresh oxygen, which is crucial for their high metabolism, especially during activities such as flight. The other options, such as directing the oxygen only to the lungs or the mouth cavity, do not account for the complexity of the avian respiratory system, while the skin does not play a role in the respiration of birds.