Tegmentum

Tegmentum
Transverse section of mid-brain at level of superior colliculi, with anterior side pointing downward. ("Tegmentum" visible center right.)
Section through superior colliculus showing path of oculomotor nerve. (Tegmentum not labeled, but surrounding structures more clearly defined.)
Details
Identifiers
Latin	Tegmentum
NeuroLex ID	Tegmentum
Anatomical terms of neuroanatomy []

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.

In embryos, the tegmentum is the anterior half of the neural tube. However, for fetuses to adults, tegmentum refers only to the parts of the brain that remain relatively unchanged after development is complete, i.e. at the brain stem especially the midbrain. Other parts, on the other hand, develop further, through folding and thickening, and have different names. Still, it is considered a continuous central region through all levels of the brainstem.