Human Anatomy - Kotsan I. Ya. 2009

Brain
Fourth ventricle

The fourth ventricle (ventriculus quartus) is derived from the cavity of the rhombencephalon and develops from the lumen of the Hindbrain vesicle. The walls of the fourth ventricle are formed by the Medulla Oblongata, Pons, Cerebellum, and the ISTHMUS OF THE rhombencephalon. In shape, the cavity of the fourth ventricle resembles a tent, comprising a floor and a roof.

The floor of the fourth ventricle is diamond-shaped (Rhomboid fossa) and is formed by the posterior (dorsal) surfaces of the medulla oblongata and the pons. The boundary between the medulla oblongata and the pons On the surface of the rhomboid fossa is marked by the medullary striae of the fourth ventricle (striae medulläres), which originate in the region of the lateral angles of the rhomboid fossa, run transversely, and sink into the median sulcus.

The roof of the fourth ventricle (tegmen ventriculi quatri) arches tent-like over the rhomboid fossa. The anterosuperior wall of this tent is formed by the superior cerebellar peduncles and the superior medullary velum (velum medulläre superius) stretched between them. The posteroinferior wall has a more complex Structure; it is composed of the inferior medullary velum (velum medulläre inferius), which laterally attaches to the peduncles of the flocculus. The tela choroidea of the fourth ventricle (tela choroidea ventriculi quatri) adheres medially to the inferior medullary velum. The latter is formed by an invagination of the pia mater into the cleft between the Inferior surface of the cerebellum above and the inferior medullary velum below. Covered on the ventricular side by an epithelial lamina, the tela choroidea forms the choroid plexus of the fourth ventricle (plexus choroideus ventriculi quatri).

The roof of the fourth ventricle contains three apertures that pierce the epithelial lamina and the pia mater of the inferior medullary velum: a single median aperture and two lateral apertures. The median aperture of the fourth ventricle (apertura mediana ventriculi quatri), or foramen of Magendie, is unpaired and located in the lower angle of the inferior medullary velum, superior to the obex. The lateral aperture of the fourth ventricle (apertura lateralis ventriculi quatri), or foramen of Luschka, is paired, smaller than the median one, and situated in the lateral angles of the inferior medullary velum. All three apertures connect the cavity of the fourth ventricle with the subarachnoid space of the Brain.

The fourth ventricle communicates with: 1) the Third ventricle via the cerebral aqueduct; 2) the subarachnoid space via the foramen of Magendie and the foramina of Luschka; 3) the central canal of the Spinal Cord via an opening located inferior to the obex. The obex (obex) is a small lamina of White matter spanning transversely above the superior end of the posterior median sulcus between the two gracile fasciculi of the medulla oblongata.