Vertebral column

From ArticleWorld

The vertebral column, also known as the spine, is the bony collection of articulated vertebrae that protect the spinal cord and maintain the structure of the human trunk. Many higher animals also have some form of a vertebral column, where it is called the back bone.

Anatomy

The vertebral column is made of 23 vertebral bodies and a distal sacrum (or tail bone). The spine itself is not completely straight. The six cervical vertebrae in the neck form a concave curvature with respect to the back. The 12 thoracic vertebrae in the upper thorax form a convex surface to the back and the 5 lumbar vertebrae form a concave curvature with respect to the lower back. The sacrum itself, at the bottom of the vertebral column, forms a convex shape with respect to the buttocks. There should be no lateral curvature in a normal spine.

No two vertebrae are alike. Each contains an anterior rounded portion called the vertebral body and spiny processes on the sides and in the back. The two processes on the side are called transverse processes and the single posterior process is called the spinous process. These projections connect muscles or ligaments to help support the back. The cervical spinous processes are short, are pointing directly toward the back and separate into two smaller processes at each end. The transverse processes often articulate with one another, one on each side of the spine.

The vertebral bodies are separated and cushioned by cartilaginous vertebral disks. The outer ring of the disk is called the annulus fibrosus. The center part is softer and has more cushioning effect. It is called the nucleus pulposus. A “ruptured disc” happens when the annulus fibrosus is breached and some of the softer pulp bulges out.

Function

The vertebral canal is formed by the hole created behind the vertebral bodies and between the articular surfaces of the various processes. This is the canal through which the spinal cord travels from the brain to the sacrum. Nerves affecting different parts of the body travel out of a space between the vertebral body and the transverse processes.

The spinous processes are a primary place in the spinal column for the attachment of muscles. In the upper back, the large trapezius muscle forms a band of connective tissue with connections to the spinous processes of the upper thorax. The latissimus dorsi muscle gradually becomes a midline sheet of tissue called the thoracolumbar fascia that connects up and down the lower spine with the spinous processes in the lower back. The latissimus dorsi muscle is one of the muscles that extend the back.

Conditions

The vertebral column can suffer a number of injuries and diseases. Arthritis can develop in the articular surfaces between the vertebral bodies or the transverse processes. The disc, as mentioned, can become damaged due to overuse or injury. Fractures of the back are rare but can happen in severe trauma. Various curvature problems of the spinal column can occur. Scoliosis happens in teens and is a result of a growth imbalance of the spine, leading to a lateral curvature. Kyphosis is an exaggerated curvature of the upper thorax seen in those with osteoporosis. Lordosis is and exaggerated curvature of the lower back, often seen as a temporary condition in pregnant women.