The midbrain is the uppermost of the three parts of the brainstem. It transitions upwards in the midbrain and downwards into the bridge. The midbrain is approx. 2 cm long. It consists of 4 main parts.

1) poster/dorsal of the four-mound plate (lamina tecti, tectum) which passes forward/ventrally into

2) the tegment part with different cores and conduction paths.

Front/ventral terminates the midbrain by
3) and 4) the so-called brain shanks (crus cerebri) one for hay. o one to the left. The cerebral canals consist of densely packed masses of nerve fibers on their way from the cerebral cortex to the bridge and on to the medulla and spinal cord. Between the two brain shanks lies the brain arm pit.

On the boundary between the four-mound plate and the tegment part, in the midline, runs the brain's water pipe that connects the 4.de and 3rd cerebral ventricles with each other. One side of the crus cerebri together with the underlying half of the tegment area is usually called the 'cerebral arm' (pedunculus cerebri).

The midbrain contains several important nuclei: various cranial nerve nuclei, the black nucleus, the red nucleus and a periaqueductal grey matter (PAG) system that surrounds the water pipe and is part of a larger pain-modifying system. The four-pile plate contains important switching stations for visual and auditory impressions.