Metencephalon

Metencephalon, hindbrain, is one of the divisions (the fifth) of the brain; it consists of the pons and cerebellum; it lies between the isthmus cerebri and myelencephalon, or medulla oblongata, forming together with it the so-called rhombencephalon, which is opposed to the prosencephalon, or forebrain. It develops from the upper part of the hindbrain vesicle, the cavity of which transforms into the fourth ventricle, narrowing upward and passing into the cerebral aqueduct of Sylvius, and downward into the spinal canal. From the anterior wall of the upper part of the hindbrain vesicle, the pons is formed, visible from the base of the brain, and from the posterior wall—the cerebellum, lying under the inferior surface of the brain but extending beyond its limits (see Pons and Cerebellum).