(sŭb-stan'sh(ē-)ă )

[L. substantia, that which underlies, essence, substance]

The material of which any organ or tissue is composed; matter. SYN: substance.

s. alba The white matter of the brain and spinal cord.

s. cinerea The gray matter of the brain and spinal cord.

s. ferruginea The elongated mass of pigmented cells in the locus coeruleus.

s. gelatinosa The three dorsal-most layers (laminae 1, 2, and 3) of cells in the dorsal horns of the spinal cord.

s. grisea The gray matter of the spinal cord.

s. innominata A region of the brain lying between the globus pallidus of the basal ganglia, i.e., the basal nuclei, and the ventral surface of the forebrain.

s. nigra A nucleus lying along the posterior surface of the cerebral peduncle in the midbrain tegmentum and closely associated with the basal nuclei. The substantia nigra sends axons to and receives axons from the striatum. The neurons of the substantia nigra that project to the striatum (via the medial forebrain bundle) use dopamine as their transmitter. Parkinson disease causes a degeneration of the dopaminergic neurons in the substantia nigra, leading to the characteristic symptoms of muscular rigidity, tremor, and reduced intentional movements SYN: locus niger.

s. ossea dentis Cementum.

s. propria of the cornea The middle of the five histologic layers of the cornea. The substantia propria of the cornea is composed of 200–250 layers, each of which contains regularly spaced parallel collagen fibers, with occasional cells.