How do birds breathe without a diaphragm?

How do birds breathe without a diaphragm?

• A. Expanding rib cage
• B. Gills
• C. Diaphragm
• D. Skin diffusion

Answer: (A)

Birds ventilate their lungs by expanding the chest cavity with the action of the rib cage and sternum, using the intercostal muscles to expand the thorax. Since they lack a true diaphragm, this rib-cage expansion creates negative pressure that pulls air into the trachea and lungs. The lungs are extended by a system of air sacs that act as bellows, moving air through the gas-exchanging tissues for efficient respiration. Gills aren’t used by birds, and there isn’t a diaphragm to contract; skin diffusion isn’t the primary method of oxygen uptake in birds.

Birds ventilate their lungs by expanding the chest cavity with the action of the rib cage and sternum, using the intercostal muscles to expand the thorax. Since they lack a true diaphragm, this rib-cage expansion creates negative pressure that pulls air into the trachea and lungs. The lungs are extended by a system of air sacs that act as bellows, moving air through the gas-exchanging tissues for efficient respiration. Gills aren’t used by birds, and there isn’t a diaphragm to contract; skin diffusion isn’t the primary method of oxygen uptake in birds.