The human spine is composed of 23-24 vertebrae and an intervertebral disc which acts as a buffer in the middle. This structure is fixed by ligaments and small spinal joints; Has the functions of supporting trunk and protecting internal organs.

The spine is artificially divided into 7 cervical vertebrae, 12 thoracic vertebrae, 5 lumbar vertebrae, sacrum and coccyx. The five sacrums and four coccyxes of human beings are fused with each other, and they are called "pseudovertebrae". Vertebrates with tails have different numbers of coccyxes.

The adult's spine bends in a double S shape in the sagittal plane, and there are four physiological bends in the lateral view of the spine: neck, chest, waist and sacrum. It provides strong support for human beings who walk upright, and it is elastic. The curvature of the spine in which the neck and waist protrude forward is called lordosis, and the opposite protrusion of the chest and tail is called kyphosis.

Extended data:

Human skeleton function

1, supporting function: different bones of human body are connected into a whole through joints, muscles, ligaments and other tissues, which support the body. If human beings have no bones, they can only be a pile of soft tissues lying on the ground, and they can't stand, let alone walk.

2. Protection: The human skeleton is like a frame, which protects the important organs of the human body, so as to avoid the "interference" and damage of external forces as much as possible. For example, the skull protects the brain tissue, the spine and ribs protect the heart and lungs, and the pelvic bones protect the bladder and uterus. Without the protection of bones, external shocks and blows can easily damage internal organs.

3. Motor function: Bones cooperate with muscles, tendons, ligaments and other tissues to achieve human motor function. Skeleton provides the necessary support for exercise, muscle and tendon provide the motive force for exercise, and the role of ligament is to maintain the stability of skeleton and make the exercise continue. Therefore, we say that bones are the basis of exercise.

4. Metabolic function: There is a close relationship between bones and human metabolism. Bone contains a lot of calcium, phosphorus and other organic and inorganic substances, and is a participant and regulator of inorganic salt metabolism in the body.

Baidu encyclopedia-human skeleton