A cross-section of the spinal cord reveals an inner H-shaped gray matter consisting of neuronal cell bodies and an outer white matter composed of myelinated neuronal axons. The ventral or anterior horns of gray matter contain cell bodies of motor neurons, whereas the dorsal or posterior horns contain cell bodies receiving sensory information (eFig. 9.47). An enlargement of the lateral portion of the gray matter, termed the intermediolateral cell column, can be seen in the T1 to L2 region of the spinal cord (eFig. 9.49). This region enlarges to accommodate the preganglionic cell bodies of the sympathetic nervous system. To further define the diverse cytoarchitecture of the gray matter, it is divided into 10 zones known as Rexed’s laminae (eFig. 9.50). These will be referred to as they relate to later discussions of the ascending and descending tracts within the spinal cord.