Snakes possess a unique respiratory system, distinctly different from that of mammals. Their elongated bodies have necessitated adaptations in how they acquire and process oxygen.
Understanding Snake Lung Anatomy
Snakes typically possess one primary functional lung, the right lung. This lung is significantly elongated, stretching far back within the anterior portion of the snake’s body cavity. While some species, such as boas and pythons, may have two lungs, the left lung is usually smaller or absent.
The functional right lung is divided into two distinct regions. The anterior section, known as the vascular lung, is where gas exchange occurs. The posterior part is a thin-walled, less vascularized air sac, often called the saccular lung, which primarily stores air. Some species also feature a “tracheal lung,” a vascularized extension of the windpipe that contributes to gas exchange.
How Snakes Breathe
Unlike mammals, snakes do not have a diaphragm to facilitate breathing. Instead, they rely on the muscles located between their ribs, known as intercostal muscles, to expand and contract their rib cage. Air is drawn into the lungs through an active process involving muscle contraction, while exhalation is largely a passive process as these muscles relax.
A specialized opening called the glottis, located behind the tongue, serves as the entrance to the trachea or windpipe. The glottis can protrude forward and to the side of the mouth. This allows a snake to continue breathing even while consuming large prey items, a process that can take a considerable amount of time. The posterior saccular part acts as an air reservoir, maintaining respiration during prolonged activities like swallowing.
Evolutionary Lung Adaptations
The elongated body form of snakes has influenced the evolution of their respiratory system. The single, extended right lung is a direct adaptation to their slender, limbless shape, providing sufficient surface area for gas exchange. This design allows for efficient gas exchange, despite the lack of a diaphragm and a compact chest cavity.
The division of the lung into a vascular, gas-exchanging region and a saccular air-storage region is another adaptation. The saccular lung serves as an air reservoir, enabling snakes to store air. This feature is particularly beneficial for aquatic species that may need to hold their breath underwater or for snakes that constrict prey, allowing them to sustain breathing even when their bodies are compressed. Studies indicate that the asymmetry in snake lungs develops early, reflecting an evolutionary modification in their body plan.