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Posterior medulla
Last reviewed: 07.07.2025
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The hindbrain and medulla oblongata were formed as a result of the division of the rhombencephalic vesicle.
The hindbrain (metencephalon) includes the bridge, located in front (ventrally), and the cerebellum, which is located behind the bridge. The cavity of the hindbrain, and along with it the oblongata, is the fourth ventricle.
The bridge (pons; Varoli's bridge) at the base of the brain stem has the appearance of a transversely located ridge, which at the top (in front) borders the midbrain (with the cerebral peduncles), and at the bottom (at the back) - with the medulla oblongata.
The dorsal surface of the pons faces the fourth ventricle and participates in the formation of its bottom - the rhomboid fossa. Laterally, it can narrow on each side and passes into the middle cerebellar peduncle (pedunculus cerebellaris medius), which goes into the cerebellar hemisphere. The border between the middle cerebellar peduncle and the pons is the exit point of the trigeminal nerve. In the deep transverse groove separating the pons from the pyramids of the medulla oblongata, the roots of the right and left abducens nerves emerge. In the lateral part of this groove, the roots of the facial (VII pair) and vestibulocochlear (VIII pair) nerves are visible.
The cerebellum (cerebellum; small brain) is located posterior (dorsal) to the pons and the upper (dorsal) part of the medulla oblongata. It lies in the posterior cranial fossa. The occipital lobes of the cerebral hemispheres hang over the cerebellum, separated from the cerebellum by the transverse fissure of the cerebrum (fissura transversa cerebralis).
The cerebellum has an upper and lower surface, the boundary between which is the posterior edge of the cerebellum, where a deep horizontal fissure (fissura horizontalis) passes. It begins at the point where the middle peduncles enter the cerebellum. The upper and lower surfaces of the cerebellum are convex. On the lower surface there is a wide depression - the cerebellar valley (vallecula cerebelli).
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