Brainstem: The brainstem includes the medulla oblongata, pons and midbrain. The caudal end of the medulla oblongata joins the spinal cord at the foramen magnum, and the cephalic end of the midbrain joins the mesencephalon. The medulla oblongata and pons lie on the slope of the skull base. Dorsal aspect of the brainstem: The medulla oblongata can be divided into upper and lower segments. The lower segment is called the closed section, and its ventricular cavity is a continuation of the central canal of the spinal cord. The median sulcus is flanked by the thin bundle nodes and the cuneate nodes, in which the thin bundle nuclei and the cuneate nuclei are hidden respectively. The dorsal surface of the pons forms the upper part of the floor of the fourth ventricle. At the base of the fourth ventricle, there is a transverse medullary stripe, which marks the demarcation between the medulla oblongata and the pons. Ventral side of the brainstem: At the median fissure of the medulla oblongata, there are left and right crossed fibers, called conus interpositus, which is the division between the medulla oblongata and the spinal cord. The longitudinal bulges on either side of the median fissure are the cones formed by the corticospinal tracts (or conus tractus). The lower end of the cerebral bridge is divided from the medulla oblongata by the pontine sulcus, and the upper end is connected to the cerebral peduncle of the midbrain.