Unlike some animals, snakes do not primarily breathe through their skin. Instead, their respiration relies on a specialized internal system, unlike amphibians that absorb significant oxygen through their skin.
The Snake Respiratory System
Snakes possess a unique respiratory system adapted to their elongated body shape. Unlike mammals, they lack a diaphragm, using muscles between their ribs to expand and contract their chest cavity for breathing. Inspiration is an active process involving muscle contraction, while expiration is passive as these muscles relax. This rib-driven mechanism is useful for constricting snakes, allowing them to breathe even when their bodies are compressed.
Most snakes have one functional lung, usually the right, with the left often reduced or absent. This elongated lung extends through much of the snake’s body. The portion closest to the head handles oxygen exchange, while the caudal part often functions as an air sac for storage, not gas exchange. This reservoir helps the snake maintain an air supply during activities like prolonged swallowing.
Air enters through external nostrils, passing through the nasal cavity to internal nostrils. From there, it reaches the glottis, a small opening behind the tongue that leads into the trachea. The trachea is a tube supported by incomplete cartilaginous “C”-shaped rings. A notable adaptation is the snake’s ability to extend its glottis out the side of its mouth while consuming large prey, ensuring continuous respiration during feeding.
Functions of Snake Skin
Snake skin serves multiple functions. It provides protection against physical damage and helps prevent water loss (desiccation). Its layered structure, composed of keratin, forms scales that offer a protective barrier. The skin also shields snakes from pathogens and helps regulate body temperature.
The skin’s coloration and patterns contribute to camouflage, helping snakes avoid predators or ambush prey. Some snakes also use their skin for thermoregulation by seeking warm or cool environments, as they are ectotherms relying on external sources for body temperature. They adjust their temperature by moving between sunny and shaded areas, or by absorbing heat from warm surfaces.
Shedding, or ecdysis, is a key function of snake skin. Snakes periodically shed their entire outer layer, including the clear scales covering their eyes, to allow for growth and remove parasites. This process occurs several times a year, more frequently for younger, growing snakes. The old skin separates as a new layer grows underneath, ensuring healthy, functional skin. While some sea snakes have a limited capacity for cutaneous respiration, this is a specialized adaptation, not the primary means of breathing for snakes generally.