(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.
sidebending and flexion/extension. The transverse ligament holds the dens against the anterior arch of the atlas. It has an upward prolongation to the occiput and a caudal extension to the posterior surface of the body of the axis, forming the cruciform ligament of the atlas. Its function is to restrict axial rotation, Fig. 1: Anatomical sketch of the atlas (1) and dens axis (2) from above, showing the atlanto-alar (3) and the occipito-alar ligaments (4) as well as the transverse (5) and the anterior atlanto-dental ligaments (6).