It is the posterior part of the central nervous system that runs mid-dorsally within the vertebral column. It is an elongated, almost cylindrical part.  It extends from the medulla oblongata through the protective bony arch of each vertebrae to the level of the second lumbar vertebra. It measures 42 to 45 cm long and 2cm thick. It is surrounded by three protective meninges:- dura mater, arachnoid and pia mater. It arises from the base of the brain and remains almost the length of the vertebral column. Below the second number vertebra, spinal nerves arise from the spinal cord.

Internally, the spinal cord is divided into left and right symmetrical halves by a posterior median sulcus and anterior median fissure. In the centre there is a central canal surrounded by a butterfly shaped area of grey mater. Around the grey matter, there is white matter. The grey matter is H shaped projecting dorsally into two dorsal and two ventral horns. The grey matter contains the bodies of neurons with tree-like branching of dendrons and neuroglial cells. The central canal contains cerebrospinal fluid. In each segment of the spinal cord, a spinal nerve arises from each side of the cord. There are 31 pairs of spinal nerves that arise from different segments of the spinal cord. Each spinal cord nerve carries both sensory and motor impulses.

 Functions of the spinal cord

i) It is the center of spinal reflex action.

 ii)Stimuli are passed from and to the brain through the spinal cord.