Spinal Cord, IV discs, and Zygapophysial Joints

Spinal Cord

The spinal cord is one of the major components of the vertebral canal.  It begins at the foramen magnum as a continuation of the medulla oblongata and continues down to vertebrae T12-L3, depending on the person.  The inferior end of the spinal cord is known as the conus medullaris.  The spinal cord runs through the vertebral canal and is protected by the spinal vertebrae.  The spinal cord is the major communication channel between the brain and the body.  It contains numerous spinal nerves that connect from it to the parts of the body.  When an impulse is sent from a specific part of the body, it travels from the nerve to the spinal cord, and then to the brain. 

The spinal cord has been at the forefront of research due to its complexity.  Researchers are working hard to find a way to reproduce the spinal cord in order to cure injuries that have occurred to the spinal cord.  When the spinal cord is severed, the nerves inferior to the lesion are no longer able to send out impulses.  This is a great devastation to the body. 

IV discs

The intervertebral discs (IV) are joints that connect the vertebral bodies of the spinal vertebrae.  IV discs are symphyses joints that allow the vertebral column to flex and permit gliding movements between the articular processes.  The intervertebral discs are composed of an outer fibrous part called the annulus fibrous, and an inner part known as the nucleus pulpous.  The nucleus pulpous has a semi-fluid nature that permits the flexibility of the spinal cord.  The CI-C2 vertebra does not contain an IV disc and L5-S1 is the most inferior IV disc location.  The thicknesses of the discs are relative to their location and the thickness is most uniform in the thoracic region.  Their relative thickness is greatest in the cervical and lumbar region. 

 Herniated discs are a common IV disc injury.  In young individuals, the vertebrae are very strong, and a lot of times the vertebrae will fracture in a fall before the discs actually rupture.  However, if there is extreme flexion of the vertebral column the disc can rupture due to an increase in turgid pressure of the nucleus pulpous.  If the nucleus pulpous is pushed to posteriorly into the annulus fibrous region then it can herniate into the vertebral canal and compress the spinal cord. 

Zygapophysial Joints            

The zygapophysial joints are synovial joints between the superior and inferior articular processes of the adjacent vertebrae.  The zygapophysial joints in the cervical region are much more loose and flexible which allows for the vast movement of the head.  The medial branches of the posterior rami of spinal nerves innervate the zygapophysial joints and each zygapophysial joint contains two nerves. 

 Zygapophysial joints can be injured and when this occurs the spinal nerves are also affected.  This causes pain along the appropriate dermatome of the spinal nerves affected and it also causes spasms in the associated myotomes (muscles that are innervated by this particular effected nerve).  Doctors rectify this situation by denervating the zygapophysical joint through sectioning or radiofrequency dissolution.