Human brain left - midsagitttal view - description brainstem

1. Comissura posterior
2. Colliculus superior
3. Tectum
4. Colliculus inferior
5. Velum medullare superior
6. Tegmentum
7. Mesencephalon - Midbrain
8. Pedunculus cerebri
9. Fossa interpeduncularis
10. Sulcus pontinus superior
11. Pons (Basilar Pons)
12. Sulcus pontinus inferior
13. Medulla oblongata
14. Pyramis medullae oblongatae

As seen in the midsagittal view, the brainstem is divided into 3 longitudinal tiers: 1) The Tectum (roof) located posterior to the cerebral aqueduct in the midbrain, 2) The Tegmentum (floor) which is located anterior to the ventricle throughout the length of the brainstem, 3) The Pyramid in the medulla, the Basilar Pons in the pons, and the Cerebral Peduncle in the midbrain are all part of a large motor pathway (Pyramidal Tract) which is located anterior to the tegmentum.

The Tectum is further divided into a Superior Colliculus and an Inferior Colliculus on each side. The Posterior Commissure of the midbrain is located just rostral to the tectum. Caudally, the tectum is continuous with the Superior Medullary Velum which forms the roof over the rostral portion of the 4th ventricle.

The Medulla is separated from the Pons by the Inferior Pontine Sulcus and the Pons is separated from the Midbrain by the Superior Pontine Sulcus.