(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 shallow depression, or furrow on the surface of an organ, such as cerebral sulcus that separates the convolutions of the cerebral hemisphere. A sulcus is usually not as deep as a fissure, but, in the terminology of anatomy, the words sulcus and fissure are often used interchangeably.ollateral sulcus one on the inferior surface of the cerebral hemisphere between the fusiform and parahippocampal gyri. sulÂ´ci cuÂ´tis the fine depressions on the surface of the skin between the dermal ridges. gingival sulcus the groove between the surface of the tooth and the epithelium lining the free gingiva.