by JOSHUA ZAVERTNIK|PT, DPT, FMS, OCS, FAAOMPT
Components and Function of the Spine
The spinal column
The spinal column consists of 24 vertebrae: 7 in the cervical spine, 12 in the thoracic spine and 5 in the lumbar spine. The sacrum is a series of 5 fused vertebrae, and the coccyx — or tail bone — consists of 3-5 fused vertebrae. Between each of the vertebrae are the intervertebral discs. The vertebrae are boney structures that are uniquely shaped based upon where in the body they are located. Typically we see the most movement in the spine at the cervical level and progressively less in the lumbar region comparatively. Each vertebra has an opening known as the spinal canal. The spinal canal runs through the middle of each vertebrae which allows for the spinal cord to pass through and also protects it.
The spinal cord
The spinal cord along with the brain is often referred to as the central nervous system (CNS). The cord itself is comprised of neural tissue that is surrounded by three layers of tissue: dura mater, arachnoid mater and pia mater. Between the arachnoid and pia mater is the cerebral spinal fluid (CSF). The spinal cord is housed with the spinal column and extends from the foremen magnum (the opening at the base of the skull) and runs the length of the spinal column and usually ends at the level of L1 or L2; this tapered lower end of the cord is known as the conus medullaris. The cord itself ends there, but the lower spinal nerves continue to traverse the rest of the spinal column to the sacrum in a tight cluster of hair-like fibers known as the cauda equine — the horse’s tail. The spinal cord consists of 31 segments, and each has a pair of spinal nerves that extend to the left and the right.
Peripheral Nervous System
Spinal nerves carry different levels of responsibility based upon their location. Once the spinal nerve extends beyond the vertebral body, it is classified as a peripheral nervous system. The peripheral system can be broken into two sub-classifications: the autonomic nervous system (ANS) and the somatic nervous system. The somatic nervous system is responsible for the voluntary motor control that we have over our bodies, while the ANS works with systems such as digestion, breathing and heart rate — things that are more automated and regulated by the body.