(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.
Both posterior and anterior gray columns are sites where sensory and motor cell bodies, respectively, are found. Ventral root: Bundle of somatic motor fibers (axons of somatic motor neurons) and preganglionic fibers (axons of autonomic motor neurons). Constitute the efferent outflow of the spinal cord. Anterior median fissure: About 3 mm deep. Contains blood vessels (anterior spinal artery) supplying the anterior two thirds of the cord. Anterior lateral sulcus: Site of exit of ventral root.