The human spine or vertebral column acts as the main support for the body and allows for movements such as rotation, bending and twisting. The spine’s dual roles of support and movement, and its complex design, make it a marvel of engineering and vulnerable to injury. This blog posting will review the basic anatomy of the spine with a follow up post on degenerative disc disease and back injuries.
The human vertebral column is made up of 33 vertebrae broken down into five regions, cervical (neck), thoracic (mid back), lumbar (low back), sacral (pelvis) and coccyx (vestigal tail).
Collectively the vertebral column acts to protect and house the spinal cord. It also acts as a segmented flexible rod that allows for our bipedal locomotion and mobility. The most flexible areas in the spine are the cervical and lumbar areas. The thoracic spine and sacrum act to stabilize the spine and interact with the ribs and pelvic bones.
Each region of the vertebral column has diagnostic characteristics that are unique to that section of the spine. For example cervical vertebrae have an extra foramen (hole) to accommodate the vertebral artery, the thoracic vertebrae have an extra facet for the articulation of the ribs and the sacrum is actually five vertebra fused together. The lumbar vertebrae are the largest and support the weight of the body.
Each section of the spine has a specific function for which it is designed. The cervical spine is responsible for holding the head up and allows for a large range of motion including rotation of the head and lateral flexion. The thoracic spine acts to protect the contents of the thorax through its articulation with the ribs. The robust lumbar vertebra act to bear the weight of the body. The sacrum forms the posterior portion of the pelvis as it articulates with the innominate (hip) bones. The small coccyx bones act as areas of attachment for important muscles and ligaments of the pelvic floor.
The human spine has four natural curves. The cervical and lumbar regions have concave curves that mimic each other. Similarly the thoracic and sacral regions have convex curves. These curves allow for movement, shock absorption and balance.
In between each of the 33 vertebrae are intervertebral discs that act as shock absorbers. Each disc has a fibrous ligamentous portion known as the annulus. Inside the annulus is the jelly like nucleus. Degenerative changes to the vertebra and the intervertebral dis will be discussed in detail in the next blog posting.
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