The spine - anatomy and diseases of the spine

The spine, also known as the vertebral column or backbone, is the central load-bearing element in the skeletal system. It supports the body and enables upright posture and movement in various directions. It also connects all other parts of the skeleton directly or indirectly. Inside the spine, the vertebral or spinal canal surrounds the sensitive spinal cord, protecting it from injury.

Viewed from the side, the spinal column appears as a double S-shape. This shape only develops after birth and is then suitable for absorbing and distributing shocks.

Structure of the spinal column

The spinal column is structured as follows:

• 7 cervical vertebrae (cervical vertebrae) of the cervical spine (cervical spine)
• 12 thoracic vertebrae (thoracic vertebrae) of the thoracic spine (BWS)
• 5 lumbar vertebrae (lumbar vertebrae) of the lumbar spine (lumbar spine)
• 5 fused sacral vertebrae (sacral vertebrae) of the sacrum (Os sacrum, sacrum)
• 4-5 rudimentary coccygeal vertebrae (coccygeal vertebrae) of the coccyx (Os coccygis)

The upper part of the spine (cervical, thoracic and lumbar spine) is movable.

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The individual vertebrae

The components of a vertebra are

• Vertebral body (corpus vertebrae)
• Vertebral arch (arcus vertebrae)
• spinous process (processus spinosus)
• two transverse processes (Processi transversi, Processi costales)
• four articular processes (processi articulares)

The first and second cervical vertebrae are exceptions.

The vertebral arch encloses the vertebral body in a horseshoe shape, so that together with the arches of other vertebrae the so-called vertebral canal/spinal canal(canalis vertebralis) is formed. The spinal cord and nerve roots are protected in this canal. The back muscles attach to the two transverse processes and the dome process.

The intervertebral discs

The 23 intervertebral discs (also called intervertebral discs or discus intervertebralis) in the human spine are elastic connecting links between two vertebral bodies (exceptions: first and second cervical vertebrae, sacral and coccygeal vertebrae).

An intervertebral disc consists of a relatively firm outer fibrous ring and a viscous gelatinous core (80 to 85 percent water) on the inside. Due to the flexibility of the intervertebral discs resulting from their structure, they allow the spine to move and absorb shocks caused by running, jumping etc. (buffer function).

As the intervertebral discs lose fluid and become thinner under load, a person's height decreases by approx. 1.5 to 2 cm during the course of the day. At night, when the strain is relieved, the intervertebral discs absorb water and nutrients again, making the person taller again in the morning.

Signs of wear and tear and incorrect loading can lead to destruction of the fibrous ring, which can result in a herniated disc (leakage of parts of the disc).

Illustration of the intervertebral discs and a herniated disc © Sebastian Kaulitzki / Fotolia

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Diseases and injuries of the spine

The spine can be affected by various diseases. These include

• degenerative changes (e.g. herniated disc)
• inflammatory rheumatic diseases (e.g. ankylosing spondylitis)
• Instabilities up to and including spondylolisthesis (spondylolisthesis)
• Deformities (e.g. scoliosis, the lateral curvature of the spine)
• Growth disorders (e.g. Scheuermann's disease)
• Tumors (chordomas)

If the spine is severely injured (e.g. due to an accident) and the spinal cord is damaged, paraplegia occurs.