Roof of the fourth ventricle ·Anterior part: formed by superior cerebellar peduncle and superior medullary velum ·Posterior part: formed by inferior medullary velum and choroid plexus of fourth ventricle 。 Three apertures Median aperture of fourth ventricle Two lateral apertures of fourth ventricle• Anterior part: formed by superior cerebellar peduncle and superior medullary velum • Posterior part: formed by inferior medullary velum and choroid plexus of fourth ventricle • Three apertures – Median aperture of fourth ventricle – Two lateral apertures of fourth ventricle Roof of the fourth ventricle