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The Spinal Column
The spinal column consists of 33 vertebrae, which are irregularly-shaped bones. Along with the cervical vertebrae, the spine also has thoracic, lumbar, and sacral vertebrae. Thoracic vertebrae, numbered T1 to T12, make up the rear portion of the rib cage. These bones get larger as you move further down the spinal column. The lumbar vertebrae support the body’s weight and have attachments to many of the muscles in the back. These five vertebrae are the largest in the spinal column.
The sacrum moves with the pelvic girdle. Children have four or five sacral vertebrae, which later fuse into one single bone in early adulthood. The coccyx, also known as the tailbone, consists of three to five bones that also fuse together in early adulthood.
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Cervical Vertebrae and Associated Nerves
Numbered C1 through C7, the cervical vertebrae are at the top of the spinal column. C1, also known as the atlas, allows you to nod your head up and down. C2, known as the axis, allows you to move your head from side to side. The spinal nerves, numbered according to the vertebrae above which they exit the spinal canal, carry messages from the spinal cord to the brain and from the brain to the spinal cord. Numbered C1 through C8, these nerves deliver messages between the brain and the cervical portion of the spinal column.
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Nerve C1, also known as the suboccipital nerve, innervates the muscles at the base of the skull. This allows for movement of the head and neck. C2 and C3 allow for motor control of the neck. They also allow you to feel pain and touch in the neck area. These nerves form many of the nerves located in the neck, most notably the lesser occipital nerve, greater occipital nerve, greater auricular nerve, and lesser auricular nerve. C3, C4, and C5 form the phrenic nerve, which controls the movement of the diaphragm. This allows humans to breathe normally.
C5, C6, C7, and C8 make up the brachial plexus, along with the first thoracic spinal nerve. The brachial plexus consists of tangled nerves that split and recombine to form the nerves in the upper back and arms. The C5 nerve root forms the dorsal scapular nerve, which allows for movement of the rhomboid muscles and levator scapulae. Spinal nerves C5, C6, and C7 form the long thoracic nerve.
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If there is damage to the cervical vertebrae and associated nerves, a loss of function occurs in the affected area. Depending on the area affected, this damage can range from minor to life-threatening. Damage to the nerves that supply the arm muscles may result in limited motion. If damage occurs to the nerve that controls the diaphragm, the diaphragm cannot rise and fall properly, making spontaneous breathing impossible.