Tegmentum Mesencephali

**Definition:** Portion of midbrain situated under the dorsal TECTUM MESENCEPHALI. The two ventrolateral cylindrical masses or peduncles are large nerve fiber bundles providing a tract of passage between the FOREBRAIN with the HINDBRAIN. Ventral MIDBRAIN also contains three colorful structures: the GRAY MATTER (PERIAQUEDUCTAL GRAY), the black substance (SUBSTANTIA NIGRA), and the RED NUCLEUS.

**Tree numbers:** - A08.186.211.132.659.413.875

**Synonyms:** - Mesencephalic Tegmentum - Midbrain Tegmentum - Tegmentum of Midbrain