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Saturday, April 25, 2015
The spine is an intricate structure of bones, muscles, and other tissues that form the posterior part of the body's trunk, from the skull to the pelvis. The centerpiece is the spinal column, which not only supports the upper body’s weight but houses and protects the spinal cord — the delicate nervous system structure that carries signals that control the body’s movements and convey its sensations to and from the brain.
The spinal column consists of 5 regions, made up of 33 bones called vertebrae.
Cervical Region – The top seven vertebrae make up the cervical region (labeled C1–C7). The first of these vertebrae supports the skull.
Thoracic Region - Each of these twelve vertebrae supports a pair of ribs (labeled T1–T12).
Lumbar Region – These are the five largest and strongest vertebrae (labeled L1–L5). This area of the spine, as well as its surrounding tissues, can cause "low back pain".
Sacral and Coccygeal Regions - The sacrum is made up of five fused vertebrae. The coccyx is made up of four fused vertebrae.
Stacked on top of one another, the vertebrae form the spinal column, also known as the spine. Each of these bones contains a roundish hole that, when stacked in register with all the others, creates a channel (the "spinal canal") that surrounds the spinal cord. The spinal cord descends from the base of the brain and extends in the adult to just below the rib cage. Small nerves ("roots") enter and emerge from the spinal cord through spaces between the vertebrae called "foramina" (singular is "foramen"), or "neuroforamina".
Because the bones of the spinal column continue growing long 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 large bundle of nerve roots was dubbed by early anatomists as the cauda equina, or horse’s tail.
The spaces between the vertebrae are maintained by round, spongy pads of cartilage called intervertebral discs that allow for flexibility in the lower back and act much like shock absorbers throughout the spinal column to cushion the bones as the body moves. Bands of tissue known as ligaments and tendons hold the vertebrae in place and attach the muscles to the spinal column.
Source: National Institute of Neurological Disorders and Stroke - Low Back Pain Fact Sheet
Last Reviewed: Apr 28, 2009
David J Hart, MD
Associate Professor of Neurosurgery
School of Medicine
Case Western Reserve University