Snake respiratory system — glottis, tracheal lung, and one functional lung
Overview of the snake respiratory tract — a glottis that shifts forward during swallowing, a long trachea carrying a tracheal lung in many species, and a single functional right lung.
General educational reference only — not clinical or veterinary advice. Anatomy varies between individual animals; consult a licensed veterinarian for any health concern.
Glottis and trachea
Air enters through the nostrils and reaches the glottis, a valve on the floor of the mouth behind the tongue sheath. During swallowing the glottis can be pushed forward past the prey, so a snake keeps breathing while a large meal is worked down. Behind it the trachea runs far along the body, supported by cartilage rings that are incomplete along the top.
One functional lung
In most snakes only the right lung is functional; the left is greatly reduced or absent, matching the long, narrow body. The cranial part of the right lung is richly vascular and carries out gas exchange, while the caudal part is a thin-walled, largely avascular sac that holds air rather than exchanging it. Many snakes, including boas and pythons, also have a tracheal lung — vascular tissue in the roof of the trachea.
Breathing with ribs
Snakes have no diaphragm. Ventilation comes from muscles that move the ribs, which run along nearly the whole trunk. Breathing is often intermittent rather than steadily rhythmic, and as in other ectotherms its rate follows body temperature and activity.
