The spine is made up of 33 vertebrae. These bones are stacked, one on top of the other, to form the spine or spinal column.
The spine is divided into 5 distinct sections:
- Cervical (neck region): composed of 7 vertebrae.
- Thoracic (chest region): composed of 12 vertebrae.
- Lumbar (lower back region): composed of 5 vertebrae.
- Sacrum (pelvic area): composed of 5 fused vertebrae.
- Coccyx (tailbone): composed of 4 vertebrae.
The individual vertebrae are donut shaped with an opening in the middle (the spinal canal ). The vertebrae are smallest in the cervical region and get larger as the spine progresses, with the lumbar vertebrae being the largest. The cervical region is the most flexible part of the spine, while the thoracic area doesn't have much movement. The lumbar vertebrae bear the brunt of the body's weight and stress. The sacral region helps distribute the body weight to the pelvis and hips.
| The vertebrae surround and protect the spinal cord, which lies in the spinal canal. Connecting one vertebra to the next are thick tissue bands called ligaments. The spinal column has joints called facet joints. The facet joints link the vertebrae together and give them the flexibility to move against each other, while providing stability to the entire spine.
Positioned between almost every vertebra are the intervertebral discs(there are no discs between the 1st and 2nd cervical vertebra and in the Coccyx). The discs function as the spine's shock absorbing system, which protects the vertebrae, spine, brain, and the nerves as they leave the spinal column. The discs also allow movement between the vertebrae. This movement enables the spine to move. The discs are composed of a central soft gel-like tissue surrounded by a tough cartilaginous outer ring. Bands from this cartilaginous ring anchor the discs in place between the vertebrae.
The intervertebral foramen are the openings between two adjacent vertebra (there are two of these openings, one on each side of the vertebrae). These openings allow the nerve fibers (nerve roots) in the spinal cord to exit the spinal canal and travel to their specific body parts. The nerves that leave the spinal cord to co-ordinate and control the body's organs and parts are the motor nerves. The sensory nerves are those nerves which carry signals and information back to the brain. The sensory nerves enter the spinal canal through the neural foramen. Both the sensory and motor nerves utilize the neural foramen.
The paraspinal muscles refer to those muscles next to the spine. These muscles support and move the spine. Besides these muscles, there are many small muscles in the back that control some part of the total movement between all the vertebrae and the rest of the skeleton.