The spinal cord is a part of the central nervous system and is a continuation of the medulla passing out of the cranial vault through the foramen Magnum. It runs continues caudally in the vertebral canal that forms from the adjacent vertebral foramina.
Simply put, the spinal cord is a bunch of nerves carrying electric signals between the brain and the rest of the body. Therefore, one of the most significant jobs of the cervical spine is the protection of the spinal cord as it advances through the neck to activate the rest of the body.
Cervical Enlargement Of The Spinal Cord
The spinal cord has a diameter of around 2 cm or 3/4th of an inch. It has a length that ranges between 16 to 18 inches or 41 to 45 cm. However, its diameter changes in the different regions because of the changes in the white and gray matter. These changes in the white and gray matter are reflected through the functions of the other areas. Typically, the cervical and the lumbar regions of the spinal cord show a larger diameter than the rest of the areas.
The spinal cord has two areas of enlargement: Cervical Enlargement and Lumbosacral Enlargement.
It is one of the two symmetrical enlargements that are occupying the segments of the plexuses of the limb. As the spinal cord is significantly shorter in length in comparison to the vertebral column, it extends from C3 to T1/T2 levels of the vertebral column. The greatest circumference of the enlargement is at the C6 level, which is approximately 38 mm. It extends from about the third to the fifth cervical to the first thoracic vertebra reaching a maximum circumference of about 38 mm. Here it is at a level of attachment with the sixth pair of cervical nerves. The cervical enlargement and the lumbar enlargement mean an increased amount of neurons in the gray matter along with axons in the white matter that serve the upper and lower limbs.
The spinal cord’s cervical enlargement is the key source of the spinal nerves helpful in contributing to the brachial plexus as they supply the upper limbs.
Causes of Cervical Enlargement
There are two regions in the spinal cord that are large enough to accommodate many nerve cells and the connections needed to process information relating to the upper and lower limbs. The expansion of the spinal cord that corresponds to the arms is known as cervical enlargement, including spinal segments C5 – T1. The spinal cord’s expansion that corresponds to the legs is called the lumbar enlargement, including the spinal segments of L2 – S3. As the spinal cord is much shorter than the vertebral column, the sacral and the lumbar nerves run from some distance away in the vertebral canal before they emerge from it. Thus, these nerves form a collection of nerve roots known as the cauda equina.
The main reason or cause of the cervical enlargement is the increased neural input and output to the upper limbs. It results from the increased volume of motor cells in the ventral horns of the grey matter. The spinal cord’s grey matter contains all the neuronal cell bodies, dendrites, axons, and nerve synapses.