The cervical enlargement of the spinal cord is primarily caused by the increased number of neurons and nerve fibers that are necessary to control the muscles of the upper limbs and to process sensory information from the head, neck, and arms.
This region of the spinal cord, located around the cervical vertebrae C4 to T1, is thicker than other sections because it contains the cell bodies of motor neurons that innervate the muscles of the arms, as well as the sensory pathways that carry information from the upper body back to the brain.
During fetal development and in response to the demands of upper limb function, there is an expansion of the spinal cord’s gray matter in this region. As the arms are used for a variety of activities, such as reaching and manipulating objects, the body requires a higher density of neural connections to coordinate these complex movements.
In summary, the cervical enlargement of the spinal cord is a natural adaptation of the nervous system that facilitates the motor control and sensory processing required for upper limb function.