a further sulcus - the sulcus limitans - along a line parallel to the median sulcus; within the floor, motor neurons are located medially of the sulcus limitans, while sensory neurons are located laterally. The elevation between the median sulcus and sulcus limitans (i.e. the region for motor neurons), is known as the medial eminence, while the lateral region (i.e. that for the sensory neurons) is known as the vestibular area. The sulcus limitans bifurcates at either end - the superior fovea cerebrally, and the inferior fovea caudally. The pons is located behind the middle and superior portion of the floor. In the superior region of the pons is the locus coeruleus, which due to its concentration of noradrenaline has a sky blue appearance, visible (in a colour closer to teal) through the floor of the ventricle, superiorly to the superior fovea. The internal part of the facial nerve bulges into the ventricle, forming the facial colliculus, in the process of looping around the abducens nucleus within the inferior region of the Pons. The medulla oblongata is located behind the inferior portion of the floor (and continues caudally of the ventricle). Medullary striae emerge via the median sulcus and run transversely across the floor to become part of the inferior cerebellar peduncle. The hypoglossal nucleus bulges into the floor, creating the hypoglossal trigone, located slightly superiorly to the inferior fovea, within the median eminence. The dorsal nucleus of vagus nerve, within the medulla oblongata, comprises cells that are spindle shaped, also creating a bulge—the vagal trigone—in the region of the floor which overlies them; this is the region inferior of the inferior fovea. Development The ventricular system including the fourth ventricle, develops from the central canal of the neural tube. Specifically, the fourth ventricle originates from the portion of the tube that is present in the developing rhombencephalon. During the first trimester of pregnancy the central canal expands into the lateral, third and fourth ventricles, connected by thinner channels. Choroid plexuses appear in the ventricles which produce cerebrospinal fluid. If the flow of fluid is blocked ventricles may become enlarged and cause hydrocephalus. Clinical significance The fourth ventricle is a common location of an intracranial ependymomal tumour. Additional images References External links - "Fourth Ventricle, Sagittal Section, Medial View" Brainstem Ventricular system de:Hirnventrikel#Vierter Ventrikel