Fourth Ventricle PDF

Fourth ventricle and cerebellum By: Dr. Mariam Atef Lecturer of Anatomy  Fourth ventricle (The cavity of the hind brain)  The Fourth ventricle The cavity of the hind brain Site: it lies infront of the cerebellum and behind the pons and...

Fourth ventricle and cerebellum By: Dr. Mariam Atef Lecturer of Anatomy  Fourth ventricle (The cavity of the hind brain)  The Fourth ventricle The cavity of the hind brain Site: it lies infront of the cerebellum and behind the pons and the upper half of the medulla (open medulla). Shape: Rhomboidal fossa when seen from behind, but Tent shaped when seen from the lateral side. It has 4 angles: Upper angle: continuous with the aqueduct of sylvius Lower angle: continuous with the central canal of closed medulla. Lateral angles: extend laterally to form the lateral recess of the 4th ventricle Tent shaped 4th ventricle Boundaries Lateral borders: Superiorly: the superior cerebellar peduncles. In the middle: the lateral angle forming the lateral recess. Inferiorly: the inferior cerebellar peduncle and the gracile and cuneate tubercles. Floor: (Diamond shaped) Medial eminence The floor is divided into 2 similar halves Vestibular area by the median sulcus , each half is divided by stria medullaris into upper pontine part and lower medullary part. Roof: Superiorly: the superior medullary In the middle: part of the cerebellum Inferiorly: inferior medullary vellum and the choroid plexus of the 4th ventricle attached to it.  Floor of the 4th ventricle Upper Pontine part Lower Medullary part Upper pontine part of the floor of 4th ventricle Lower Medullary part of the floor of 4th ventricle = Dorsal surface of open medulla It forms the lower part of the floor of the 4th ventricle. Separated from back of pons by the medullary stria. It shows a Posterior median sulcus, lateral to it lies the inferior fovea (a small inverted v shaped depression). On each side, the inferior fovea divides the medullary part into 3 triangular areas, from medial to lateral: Hypoglossal trigone: overlies Hypoglossal nerve nucleus. Vagal trigone: overlies Dorsal nucleus of Vagus nerve. Vestibular area: overlies Inferior and Medial Vestibular nuclei. Roof of the 4th ventricle  The roof of the 4th ventricle In its upper part: The medial borders of the 2 superior cerebellar peduncles The superior medullary vellum Vermis of cerebellum cover the superior medullary velum In its lower part: Vermis of cerebellum Inferior medullary velum Lower area consists of ependyma and pia mater in contact with each other, This thin area is invaginated into the cavity of the ventricle by the choroid plexus of the 4th ventricle. The lowest part of this area of the roof is pierced by a wide median aperature (foramen of Magendi) which connects the 4th ventricle to the subarachnoid space. Choroid plexus of the 4th ventricle it is attached to the inferior medullary velum, Shape: T-shaped , supplied by a branch from the Posterior inferior cerebellar artery (PICA)  Recesses of the roof of 4th ventricle Median recess 2 lateral recesses  Communications of the fourth ventricle At its upper angle: with the 3rd ventricle through the aqueduct of Sylvius At its lower angle: with the central canal of the closed medulla and spinal cord. With the subarachnoid space: through foramen of Magendie and foramina of Luschka  Put (T) or(F) 1- The fourth ventricle is the cavity of the cerebral hemispheres ( ) 2- The floor of the 4th ventricle is formed by the back of midbrain and pons ( ) 3- Abducent nerve emerges from back of midbrain ( ) 4- The trochlear nerve is the only cranial nerve that arise from the dorsal aspect of the brain stem ( ).