Snakes, despite their limbless bodies, possess a backbone, classifying them as vertebrates. This internal skeletal structure is shared with mammals, birds, fish, and other reptiles. Snakes have an intricate skeletal system that allows for their agility and diverse movements.
Understanding the Backbone
A backbone, or vertebral column, is a series of interconnected bones called vertebrae that extend from the skull to the tail. This central support structure provides rigidity and shape to the organism. Within this column, the delicate spinal cord is housed and protected, a crucial pathway for nerve signals.
The vertebral column also serves as an attachment point for muscles, enabling movement. Each vertebra consists of a solid, disc-shaped central part, known as the centrum, and a neural arch that encloses the spinal canal. This design provides a balance of strength and flexibility, allowing for motion while maintaining structural integrity.
The Snake’s Specialized Spine
The snake’s vertebral column is very long and contains a high number of vertebrae compared to most other animals. While humans have around 33 vertebrae, a snake can possess anywhere from 175 to over 400, with some species exceeding 600. This contributes to their extensive flexibility. Unlike other vertebrates, a snake’s vertebrae are largely uniform along its body, lacking the distinct regional specialization (like cervical, thoracic, and lumbar sections) found in many other animals.
Each vertebra connects to the next through complex joints, including a ball-and-socket joint. Additional articulations, such as zygapophyses, zygosphenes, and zygantra, provide stability while allowing for a wide range of motion in various directions. Nearly every vertebra from behind the head to the cloaca has a pair of ribs. These ribs are not connected by a sternum, allowing them to move independently and expand, which is important for swallowing large prey and enabling their movement.
Movement and Mobility
The specialized structure of a snake’s spine, with its numerous flexible vertebrae and unattached ribs, facilitates its diverse methods of locomotion. Powerful muscles run along the body, connecting vertebrae and ribs, allowing precise control over each segment. This intricate muscular system enables snakes to bend and undulate in complex patterns, propelling them across terrains.
One common movement is lateral undulation, or serpentine locomotion, where the snake moves in an S-shaped curve, pushing against surface irregularities. In constricted spaces, snakes may use concertina movement, where they bunch up parts of their body to anchor themselves and then extend the rest forward. Sidewinding is an adaptation for loose or sandy surfaces, involving lifting sections of the body and throwing them sideways. Larger snakes often employ rectilinear motion, a slow, caterpillar-like movement where broad belly scales grip the ground and muscles pull the body forward.