The main parts of a snake's skeleton are (1) the skull, (2) vertebrae, and (3) ribs. A few snakes, such as blind snakes, boas, and pythons, have vestiges of hind legs or hipbones.

Skull. The bones of a snake's skull are loosely connected, but the brain is completely enclosed by bone.

In most snakes, the lower jaw has two bones connected at the chin by an elastic tissue. These bones can be stretched widely apart. The lower jaw is loosely attached to the upper jaw. Several bones of the upper jaw and roof of the mouth also are loosely joined to one another and to the rest of the skull.

Some bones of the lower and upper jaws have pointed teeth that curve back toward the throat. These teeth are not suitable for chewing, so snakes swallow their prey whole.

The two sides of a snake's jaw can be moved separately. The structure of their jaws enables most snakes to open the mouth widely and swallow animals that are larger than their own head. To swallow an animal, a snake moves first one side of its jaws forward and then the other side. The snake's teeth stick into the prey and prevent it from escaping. As the snake alternately draws each side of its jaws backward, it pulls the animal toward the throat.

Vertebrae. Snakes have about 150 to over 400 vertebrae, depending on the species. (By comparison, humans have only 32 or 33 vertebrae in their backbones.) Strong, flexible joints connect the vertebrae and enable the body to make a wide range of movements. In general, the more bones a snake has in its backbone, the more agile it is.

Ribs. A pair of ribs is attached to each vertebra in front of the tail. The ribs are not joined together along the belly and so can be extended outward, allowing the snake to swallow bulky prey.