The centerpiece is the spinal column, which supports the upper body’s weight and houses and protects the spinal cord. Stacked on top of one another are more than 30 bones (the vertebrae) that form the spinal column or spine. Each of these bones contains a roundish hole that, when stacked in register with the others, creates a channel that surrounds the spinal cord.
The spinal cord descends from the base of the brain to just below the rib cage. Small nerves (roots) enter and emerge from the spinal cord through spaces between the vertebrae.
Because the bones of the spinal column continue growing after the spinal cord reaches its full length in early childhood, the nerve roots to the lower back and legs extend many inches down the spinal column before exiting. This bundle of nerve roots is known as the cauda equina, or the "horse’s tail".
Other Structures of The Back
Spaces between the vertebrae contain round, spongy pads of cartilage called intervertebral discs that allow for flexibility in the lower back. Bands of tissue known as ligaments and tendons hold the vertebrae in place and attach the muscles to the spinal column.
Starting at the top, the spine has 4 regions:
- 7 cervical (neck) vertebrae
- 12 thoracic (upper back) vertebrae
- 5 lumbar vertebrae
- the sacrum and coccyx (tailbone)
The lumbar region of the back, where most back pain is felt, supports the weight of the upper body.