(Botany) an association of a fungus and a plant in which the fungus lives within or on the outside of the plant's roots forming a symbiotic or parasitic relationship. See ectotrophic mycorrhiza, endotrophic mycorrhiza. [C19: from myco- + Greek rhiza root]
Medical Definition of POSTERIOR MEDIAN SULCUS. : a shallow groove along the midline of the posterior part of the spinal cord that separates the two posterior funiculi and is the external boundary of the posterior median septum. a shallow groove along the midline of the posterior part of the spinal cord that separates the two posterior funiculi and is the external boundary of the posterior median septum.
The central sulcus lies approx. midway along the lateral surface of the cerebral hemisphere, between the frontal and occipital poles of the brain. The gyrus anterior to the central sulcus -- the precentral gyrus -- is the primary motor cortex, and the gyrus posterior to the central sulcus -- the postcentral gyrus -- is the primary sensory cortex. Occasionally, the central sulcus is interrupted and is not a continuous groove from top to bottom.