The hind-brain or rhombencephalon occupies the posterior fossa of the cranial cavity and lies below a fold of dura mater, the tentorium cerebelli. It consists of
- the myelencephalon, comprising the medulla oblongata and the lower part of the fourth ventricle;
- the metencephalon, consisting of the pons, cerebellum, and the intermediate part of the fourth ventricle;
- the isthmus rhombencephali, a constricted portion immediately adjoining the mid-brain and including the superior peduncles of the cerebellum, the anterior medullary velum, and the upper part of the fourth ventricle.