The part of the midbrain (mesencephalon) that backwards/dorsally transitions into the four-headed plate (lamina tecti) and forward/ventral into the cerebral peduncles (crus cerebri).
Tegmentum(Latin)= cover, "roof", and refers to the part of the mesencephalon that covers the two crus cerebri.
The metabrain tegment part contains cranial nerve nuclei, conduction pathways and formatio reticularis upper part and passes downwards into the temporal part of the bridge (pons), which in turn turns downwards into the medulla oblongata part of the medulla .