The spine, or spinal column, consist of bone and is the primary support of the skeleton in vertebrates. It protect the spinal cord and the roots of the spinal verves, while allowing flexibility. The spine is the point of attachment for the skull, ribs, pelvis, muscles, and ligament.

In humans the flexible part of the spine, or backbone consist of 24 separate vertebrate held together by strong ligaments; 7 in the neck (vertical vertebrae), and 5 in the lower back (lumbar vertebrae). The sacrum, located below the lumbar vertebrae and joined to the pelvis, cosist of 5 fused vertebrae. The coccyx, or tailbone, is below the sacrum and consist of 3 to 5 fused, rudimentary vertebrae. Each vertebra has two parts; a short, solid, cylindrical structure called the body or centrum, and the vertebral or neural arch. In the center of each arch is a large hole, or foramen, which is continuous and protects the spinal cord. Spinal fluid circulates within the foramen. Spinal nerves pass from the cord through notches in the vertebral arch.

A bony bony projection extends from each side of the vertebral arch, a projection in the middle of the arch may be seen a felt through the skin. Thoracic vertebrae have surface for attachment of ribs. The vertebral bodies are separated from each other by cartilaginous pads called intervertebral disks.

The spine is subject to structural defects such as scoliosis, infections, diseases such as arthritis or cancer, and traumatic injuries, such as broken vertebrae, which can result in serious damage. The intervertebral disks can also bulge and press on nerves, causing pain. These problems may respond to physical therapy, but surgery a sometimes necessary.


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