Substantia alba medullae spinalis

In cross-section, the peripheral region of the cord contains neuronal white matter tracts containing sensory and motor axons.

Internal to this peripheral region is the grey matter, which contains the nerve cell bodies arranged in the three grey columns that give the region its butterfly-shape.

This central region surrounds the central canal, which is an extension of the fourth ventricle and contains cerebrospinal fluid.

The spinal cord is elliptical in cross section, being compressed dorsolaterally.

Two prominent grooves, or sulci, run along its length.

The posterior median sulcus is the groove in the dorsal side, and the anterior median fissure is the groove in the ventral side.