(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.
Gray's Fig. 727 - Medial surface of left cerebral hemisphere. In neuroanatomy, a sulcus (Latin: furrow, pl. sulci) is a depression or groove in the cerebral cortex. It surrounds a gyrus (pl. gyri), creating the characteristic folded appearance of the brain in humans and other mammals. 1 Structure.