Anatomy of the spine

Cervical Region

This area contains seven vertebrae, numbered C1 through C7. The topmost vertebra, C1, is referred to as the atlas, while C2 is known as the axis. These two specialized bones work together to create the articulation between the skull and the spine, enabling rotational and nodding movements of the head.

Thoracic Region

The thoracic section is situated in the upper-to-middle back and contains twelve vertebrae, labeled T1 through T12. These bones provide anchoring points for the ribs, forming the posterior support for the chest cavity.

Lumbar Region

The lumbar spine, commonly known as the lower back, consists of five vertebrae, L1 to L5. This segment bears the majority of the body's weight, making it the primary weight-bearing section of the entire spinal column.

Sacral Region

The sacral region features five fused vertebrae, numbered S1 through S5. Together, they solidify into a single bony structure called the sacrum, which connects to the pelvic bones and provides a strong foundation for the pelvis.

Coccygeal Region

The coccygeal area, often called the tailbone, is made up of four small vertebrae. These tiny bones may be either fused together or remain separate. They form the coccyx, which serves as an anchor for several muscles, tendons, and ligaments, and also provides support when a person is seated.

Vertebrae

Across all five regions, the vertebrae collectively uphold the body's mass and safeguard the spinal cord and its nerve roots. Each individual vertebra possesses intricate structural components that contribute to the overall function and flexibility of the spine.

Lumbar vertebra

Vertebral Body

The primary component of a vertebra is the vertebral body—a cylinder-shaped mass of bone located at the front of the bone. This structure carries the bulk of the weight placed on the spine.

Vertebral Canal

Positioned behind the vertebral body is the vertebral canal, a protective passageway through which the spinal cord travels from the brain down the back.

Spinal Cord

The spinal cord is the major bundle of nerve tissue that transmits signals between the brain and the rest of the body. Its termination point is near the L1 and L2 vertebrae, where it branches into a cluster of nerve roots known as the cauda equina.

Nerve Roots

On each side of the spine, nerve roots emerge as thick nerve branches. These roots relay messages between the spinal cord and the arms, legs, and other parts of the body, enabling both movement and sensation.

Pedicles

Flanking the sides of the vertebral canal are the pedicles—small bony bridges that connect the front vertebral body to the rear arch of the vertebra, helping to form the protective ring around the spinal cord.

Lamina

The laminae are flat bony plates that create the rear protective wall of the vertebral canal. They cover and shield the spinal cord from behind, adding an extra layer of safety.

Spinous Process

Extending backward from the lamina is the spinous process—a prominent bony projection that can be felt along the midline of the back. It acts as an anchor for muscles and ligaments that control spinal movement and stability.

Transverse Processes

Projecting outward from each side of the vertebra are the transverse processes. These bony protrusions also serve as attachment sites for the muscles and ligaments responsible for moving and stabilizing the spine during daily activities.

Articular Facet

The articular facets form the joints where adjacent vertebrae connect with one another. Each vertebra has four facets—two facing upward (superior) and two facing downward (inferior). These facet joints are lined with smooth cartilage, which permits friction-free movement and allows the spine to bend and twist.

Intervertebral Disc

Sandwiched between the vertebral bodies are the resilient, flexible spinal discs. These discs act as shock-absorbing cushions that permit bending, twisting, and overall spinal flexibility. Each disc has a tough outer ring, called the annulus fibrosus, and a soft, gel-like inner core, known as the nucleus pulposus.