(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.
2 median grooves: A deep anterior median fissure and a shallow posterior median sulcus. These extend length of cord forming lateral halves. anterior median fissureposterior median sulcus DRAW! The basic structures of the spinal cord show lateral symmetry, with white matter on the outside and gray matter on the inside. median grooves: A deep anterior median fissure and a shallow posterior median sulcus. These extend length of cord forming lateral halves. anterior median fissureposterior median sulcus DRAW! The basic structures of the spinal cord show lateral symmetry, with white matter on the outside and gray matter on the inside.