midbrain tegmentum
midbrain tegmentum
"Ventral part of the midbrain, separated from the hindbrain by the isthmus[ISBN:0471888893]. Subdivision of the midbrain lying anterior to the tectum and posterior to the substantia nigra and cerebral peduncle[FMA] The part of the midbrain extending from the substantia nigra to the cerebral aqueduct in a horizontal section of the midbrain. It forms the floor of the midbrain that surrounds the cerebral aqueduct[WP]."