A snake breathes through a small opening located right behind the tongue called the glottis. The glottis leads to the trachea and remains closed until the snake takes a breath.
When a snake hisses, a small piece of cartilage vibrates, giving the snake its signature sound. A snake has the ability to extend its glottis while it eats, which allows it to breathe while eating. Since a snake does not have a diaphragm like mammals, it breathes by contracting muscles located between the ribs. Like mammals, snakes have two lungs. One lung, the one closest to its head, is responsible for oxygen exchange. The lung closest to the snake's tail is an air sac.