Fourth Ventricle and Cerebellum 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 ( ). cerebellum By: Dr. Mariam Atef Lecturer of Anatomy It is the largest part of the hind brain, located in the posterior cranial fossa.  Hind brain includes Pons, Medulla and Cerebellum Cerebellum is the largest part of the hind brain, located in the posterior cranial fossa. Tentorium cerebelli (fold of dura mater) Cerebellum Vermis: is a narrow median part joining the 2 cerebellar hemispheres (Very wide and is related to the back of the brain stem) (narrower and recieves the falx cerebelli)  1- Anatomical divisions  Thus, Anatomically, the Cerebellum consists of 3 lobes: 1- Anterior lobe: lies infront of the primary fissure. 2-Posterior lobe: lies between the primary fissure and the posterolateral sulcus. 3- Flocculonodular lobe: formed of the 2 flocculi and nodule in the middle.  Functional divisions Cerebellum is divided into 3 functional zones Vestibulocerebellum Cerebro-cerebellum (Archicerebellum) (Neo-cerebellum) Spino-cerebellum Flocculonodular lobe The remaining large part (Paleocerebellum) of the cerebellum Vermal and paravermal zone Concerned with equilibrium Concerned with planning and control of movements Concerned with regulation of the muscle tone and muscle coordination So, Functions of the cerebellum: 1- Maintains Equilibrium. 2- Regulation of muscle tone. 3- Planning of movements and Co-ordination of the skilled movements of the body Blood supply of cerebellum: 1- Superior cerebellar artery: arise from basilar artery 2- Anterior inferior cerebellar artery: from basilar artery 3- Posterior inferior cerebellar artery (PICA): arise from vertebral artery  MCQ’S 1- The fissure which separates the superior surface from the inferior surface of cerebellum is called: A- Primary fissure B- Postero-lateral fissure C- Horizontal fissure D- Anterior median fissure 2- The fissure that separates the anterior lobe from the posterior lobe of the cerebellum: A-Postero-lateral fissure B-Primary fissure C- Horizontal fissure D- Anterior median fissure Put (T) or (F) 1- The cerebellum is separated from the cerebral hemisphere by the Tentorium cerebelli ( ) 2- The anterior notch of the cerebellum lodges the falx cerebelli. ( ) 3- Primary fissure presents in the inferior surface of the cerebellum ( ) 4- Posterolateral fissure separates between the posterior lobe and flocculonodular lobe of cerebellum ( ) 5- The superior surface of cerebellum is globular ( )