Some adaptations snakes have made to having a long, limbless body are internal organs that are arranged very differently than those of other animals. For example, one lung is usually much larger than the other. In some snakes, the smaller lung barely functions.
Instead of lying side by side, the kidneys, ovaries and testicles are arranged one behind the other. The right organ is usually in front of the left and is usually the larger of the two; these organs are also elongated. Some organs, such as the urinary bladder, have been eliminated.
Since the snake has no limbs for its spinal column to support, nearly all of its many vertebrae are alike. A snake can have as many as 400 vertebrae, and they interlock to make the spinal column strong and the snake extremely flexible.
One of the most notable adaptations is in the snake's head. Instead of a solid jawbones, the snake has bones that are loosely joined by ligaments and can articulate in ways that allow the animal to swallow prey much larger than its head. The snake's teeth are made only for gripping its prey and cannot chew. They are loosely arranged in the head, fall out easily and are replaced throughout the animal's life.