What is the air sac in a snake used for?

The air sac in a snake, also known as a lung, is primarily used for respiration. Snakes typically have a single functional lung, which can be elongated and may have an air sac that allows for efficient gas exchange. This adaptation enables snakes to maintain their metabolic needs, especially during activities like hunting or escaping predators. Additionally, the air sac can aid in buoyancy when swimming.