=====Inferior medullary velum=====
The inferior medullary velum (posterior medullary velum) is a thin layer of white substance, prolonged from the white center of the cerebellum, above and on either side of the nodule; it forms the infero-posterior part of the fourth ventricle.

Somewhat semilunar in shape, its convex edge is continuous with the white substance of the cerebellum, while its thin concave margin is apparently free; in reality, however, it is continuous with the epithelium of the ventricle, which is prolonged downward from the posterior medullary velum to the taeniae.

{{::foramen_of_magendie.jpg|}}

Fm: [[Foramen of Magendie]]; imv: [[inferior medullary velum]]; icp: [[inferior cerebellar peduncle]]; pica: [[posterior inferior cerebellar artery]] (third and forth segments) tc: [[tela chorioidea]]; tvj: telovelar junction ( yellow discontinous line).
----
[[Blake's pouch cyst]] is a cystic appearing structure that represents posterior ballooning of the [[inferior medullary velum]] into the [[cisterna magna]]