The medulla oblongata (myelencephalon), the most caudal segment of the brainstem, appears as a conical expansion of the spinal cord. The roof plate of both the pons and the medulla is formed by the cerebellum and a membrane containing a cellular layer called the choroid plexus, located in the fourth ventricle. Cerebrospinal fluid entering the fourth ventricle from the cerebral aqueduct passes into the cisterna magna, a subarachnoid space surrounding the medulla and the cerebellum, via openings in the lateral recesses in the midline of the ventricle. At the transition of the medulla to the spinal cord, there are two ...(100 of 37287 words)