The external surface of the spinal cord is marked by a number of fissures and sulci (Fig. 2.54):
The anterior median fissure extends the length of the anterior surface.
The posterior median sulcus extends along the posterior surface.
The posterolateral sulcus on each side of the posterior surface marks where the posterior rootlets of spinal nerves enter the cord.
Internally, the cord has a small central canal surrounded by gray and white matter: