from The American Heritage® Dictionary of the English Language, 4th Edition
- n. See tegmen.
- n. A part of the midbrain consisting of white fibers running lengthwise through gray matter.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The ventral portion of the midbrain, divided from the tectum by the cerebral aqueduct and the periaqueductal grey
- n. Containing the following nuclei: red nucleus, substantia nigra, ventral tegmental area
from the GNU version of the Collaborative International Dictionary of English
- n. A covering; -- applied especially to the bundles of longitudinal fibers in the upper part of the crura of the cerebrum.
from The Century Dictionary and Cyclopedia
- n. The outer porous layer of the shell of polyplacophorous mollusks or chitons, which covers the inner porcelanous articulamentum.
- n. In botany, the scaly coat which covers the leaf-buds of deciduous trees; also, one of the scales of such covering.
- n. In anatomy, the larger and deeper or upper of two parts into which each crus cerebri is divisible, separated from the crusta by the substantia nigra.
The principal gray masses of the tegmentum are the red nucleus and the interpeduncular ganglion; of its fibers the chief longitudinal tracts are the superior peduncle, the medial longitudinal fasciculus, and the lemniscus.
They are called the caudate nucleus and the tegmentum.
The caudate is a reward center of the brain, and the tegmentum is a region of the brain stem that sends dopamine to it; dopamine tracks how rewarding something is.
The tectospinal fasciculus which comprises the major part of the ventral longitudinal bundle passes down through the tegmentum and reticular formation of the pons and medulla oblongata ventral to the medial longitudinal bundle.
The axons come from large cells in the stratum opticum and stratum lemnisci and sweep ventrally around the central gray matter of the aqueduct, cross the raphé in the fountain decussation of Meynert and turn downward in the tegmentum in the ventral longitudinal bundle.
From this nucleus the fibers pass forward through the tegmentum, the red nucleus, and the medial part of the substantia nigra, forming a series of curves with a lateral convexity, and emerge from the oculomotor sulcus on the medial side of the cerebral peduncle.
Dorsally, it is partly separated from the gray substance of the quadrigeminal bodies by the fibers of the lemniscus; ventral to it are the medial longitudinal fasciculus, and the formatio reticularis of the tegmentum.
The red nucleus is situated in the anterior part of the tegmentum, and is continued upward into the posterior part of the subthalamic region.
From the cells of the gray nucleus, fibers are prolonged through the inferior brachium into the tegmentum of the cerebral peduncle, and are carried to the thalamus and the cortex of the temporal lobe; other fibers cross the middle line and end in the opposite colliculus.
The dorsal part is named the tegmentum; the ventral, the base or crusta; the two bases are separated from each other, but the tegmenta are joined in the median plane by a forward prolongation of the raphé of the pons.