Floor of 4th ventricle is not formed by ?
Floor of the fouh ventricle is not formed by Anterior medullary velum.Anterior medullary velum forms the roof.All the other options are associated with the floor of the ventricle. Fouh ventricle: It is a tent like structure, it is situated in front of the cerebellum and behind the pons and upper half of the medulla oblongata. It is lined by ciliated epithelium. Communications: 1. Cerebral aqueduct (of Sylvius): in the superior median plane (superior angle), it communicates with third ventricle. 2. Central spinal canal: in the inferior median plane (inferior angle). Boundries: 1. Roof consists of Upper poion of roof: The superior peduncle and the anterior medullary velum; Lower poion of roof: The posterior medullary velum, the epithelial lining of the ventricle covered by the tela chorioidea inferior and the taeniae of the fouh ventricle. 2. Floor: Upper pa :Fascial colliculus on the dorsal surface of pons. Intermediate pa:Vestibular nuclei medulllary striae. Lower pa:Upper pa of medulla oblongata containing hypoglossal and vagal triangles. 3. Laterally: bounded by superior and inferior cerebellar peduncles,gracile tubercle and cuneate tubercle. Apeures: Through these, the CSF leaves the fouh ventricle to the subarachnoid space One median foramen (foramen of Magendie): in the lower pa of the inferior medullary velum. Two lateral foramens (foramens of Lushka): one in each lateral recess. Ref: 1. Color atlas of neuroscience: neuroanatomy and neurophysiology, By Ben Greenstein, Adam. Greenstein, Page 16 2. BD Chaurasia's Human Anatomy,Volu III, 4Th edition, Page 397
Sulcus limitans
Anterior medullary velum
Posterior surface of pons
Posterior surface of medulla