The spine is made up of individual bones called vertebrae. In humans, there are typically 33 vertebrae, which are categorized into five regions: cervical (7 vertebrae in the neck), thoracic (12 vertebrae in the upper and mid-back), lumbar (5 vertebrae in the lower back), sacral (5 fused vertebrae forming the sacrum), and coccygeal (4 fused vertebrae forming the coccyx or tailbone).

Between each pair of vertebrae, there is an intervertebral disc made of cartilage. These discs act as shock absorbers, provide flexibility, and allow for movement between adjacent vertebrae.

The spinal cord is a long, cylindrical bundle of nerves that extends from the brainstem down the vertebral canal. It serves as the main communication pathway between the brain and the rest of the body, transmitting sensory information and motor signals.

Nerve roots branch off from the spinal cord and exit the spine through openings between adjacent vertebrae. These nerves supply different areas of the body and are responsible for motor control and sensation.

The spinal canal is the hollow space within the vertebrae that houses and protects the spinal cord.

Ligaments are fibrous tissues that connect bones, providing stability to the spine. Tendons connect muscles to bones, facilitating movement.

The spine has natural curvatures that contribute to its overall flexibility and strength. There are four primary curves: cervical lordosis (concave inwards in the neck), thoracic kyphosis (convex outward in the upper back), lumbar lordosis (concave inwards in the lower back), and sacral kyphosis (convex outward in the sacral region).