CHAPTER 1
A�ATOMY OF THE SPI�E
The spine consists of ( bones ) vertebrae that encircle and protect the spinal cord . These vertebrae are responsible for allowing the spine to move while protecting the spinal cord . To allow for movement and stability , the vertebrae interlock with one another with a joint on either side , one on the left and one on the right . The vertebrae are also separated from one another by intervertebral discs .
The discs are made of a type of cartilage . The disc is made up of a soft , gellike centre , called the nucleus pulposus , and this gel is kept in position by a tough outer fibrous layer called the annulus fibrosus . The vertebrae of the spine are further kept in position by an array of ligaments . Muscles attach to the vertebrae and nerves leave the spinal canal , formed by the vertebrae , through small openings called the neural foramina . There are 7 neck ( cervical ) vertebrae , 12 chest ( thoracic ) vertebrae , 5 lower back ( lumbar ) vertebrae and 5 sitting bone ( sacral ) vertebrae . The sacral vertebrae are fused into a single mass called the sacrum or sitting-bone .
It is unusual for the thoracic ( chest ) spine to undergo wear and tear changes as it is stabilised by the rib cage that is attached to it . The cervical ( neck ) spine and the lumbar ( lower back ) spine , on the other hand , are subject to a lot of movement and this is where most of the wear and tear takes place . The lower part of the neck where it attaches to the rigid thoracic spine , stabilised by the ribs , is under a lot of biomechanical stress . The same is true for the lumbar spine . The bottom end of the lumbar spine is attached to the sitting-bone and the pelvis , which is rigid . The same types of mechanical stresses are found here as well as where it attaches at the top to the thoracic spine .
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