Do Snakes Have Bones?

Saint Paul snake

Snakes are known for their slithering movements and extreme flexibility. Because snakes are able to coil themselves up into such tight knots or balls, you may be surprised to learn that they actually have bones. Their extreme flexibility is because their bones are structured in a very different way from those of humans.

Comparing Backbones
To get an idea of how snakes can coil up so tightly, you only need to consider the number of vertebrae they have. As in humans, their vertebrae are attached to their ribs and this creates the backbone. Snakes have somewhere from 200 to 400 vertebrae. Every vertebra has two ribs that attach to it although the tail doesn’t have any ribs. As a comparison, humans only have 24 ribs and 33 vertebrae. Because snakes have so many more vertebrae and ribs, these bones are smaller, allowing the reptile to bend in many more positions than we can. The vertebrae have bony projections along the rear and front of the backbone so the end vertebrae stay in position.

Different Rib Construction
The differences to human vertebrae don’t end with number or size. Instead of joining, snakes’ ribs have free ends. This is what lets them ingest large food or compress larger prey; it also helps that they don’t have a breastbone. Picture a cobra creating its iconic hood; this involves pulling the top ribs upwards. Similarly, the hognose snake can pull its ribs in and flatten itself as a form of defense.

Other Bones
In addition to the backbone in snakes, these animals also have a skull. The skull contains a jawbone with their teeth. The specialized jawbones are attached to the snake’s skull very loosely via stretchy ligaments. These let the animal fit large prey inside. There are actually four different components of the jaw and each can move individually. While humans can only move their jaws vertically, this allows snakes to do so horizontally as well. This gives snakes the ability to “walk” prey into their mouths.

More On Snake Anatomy
In addition to the bones, snakes also have incredibly strong muscles which they use to suffocate their prey. The bones and muscles work together to protect their internal organs. Their stomach is very long and can stretch as large as anything the snake eats. They also have a very long throat, long liver, two long lungs, intestines, and kidneys. Certain snakes, including boa constrictors and pythons, also have the remnant of hind legs. These are referred to as pelvic spurs and are accompanied by small internal bones within their pelvic area. These vestigial legs are more common and pronounced in males, who use them during mating.

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