(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.
A deep sulcus (anterior median fissure) runs on the ventral side of the spinal cord. Its dorsal counterpart is the rather flat posterior median sulcus. Laterally on both sides of the anterior median fissure the anterolateral sulci mark the exits of the anterior roots.The posterior roots enter the spinal cord through the posterolateral sulci on the dorsal side.The spinal ganglia which contain the perikarya (cell bodies) of the sensory neurons are located within the posterior roots.he posterior roots enter the spinal cord through the posterolateral sulci on the dorsal side. The spinal ganglia which contain the perikarya (cell bodies) of the sensory neurons are located within the posterior roots.