(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.
Roughly parallel and anterior to the central sulcus is the Precentral Gyrus (also called the motor strip). The precentral gyrus represents the primary motor cortex. This motor cortical area contains motor neurons whose axons extend to the spinal cord and brain stem and synapse on motor neurons in the spinal cord.