The Collaborative International Dictionary
Tegmentum \Teg*men"tum\, n.; pl. Tegmenta. [L., a covering.] (Anat.) A covering; -- applied especially to the bundles of longitudinal fibers in the upper part of the crura of the cerebrum.
Wiktionary
n. 1 The ventral portion of the midbrain, divided from the tectum by the cerebral aqueduct and the periaqueductal grey 2 Containing the following nuclei: red nucleus, substantia nigra, ventral tegmental area
Wikipedia
The tegmentum (from Latin for "covering") is a general area within the brainstem. It is located between the ventricular system and distinctive basal or ventral structures at each level. It forms the floor of the midbrain ( mesencephalon) whereas the tectum forms the ceiling. It is a multisynaptic network of neurons that is involved in many unconscious homeostatic and reflexive pathways. It is a motor center that relays inhibitory signals to the thalamus and basal nuclei preventing unwanted body movement. The tegmentum area includes various different structures, such as the "rostral (=frontal/cranial/oral) end of the reticular formation, several nuclei controlling eye movements, the periaqueductal gray matter, the red nucleus, the substantia nigra, and the ventral tegmental area."
The tegmentum is the location of several cranial nerve (CN) nuclei. The nuclei of CN III and IV are located in the tegmentum portion of the midbrain. The nuclei of CN V to VIII are located in the tegmentum at the level of the pons. The nuclei of CN IX, X, and XII are located in that of the medulla.
Usage examples of "tegmentum".
The hellfloor was a crazy-quilt of living tissues, hides, mantlings and tegmenta: wet, barnacly stretches yielded to tough knolls and swales of plated scale that reeked like a bull Titanoplod in rut, these in turn yielding to meadows of black thorns as thick as fur.