| fenestra rotunda | An opening on the medial wall of the middle ear leading into the cochlea, closed in life by the secondary tympanic membrane. Synonym: cochlear window, fenestra of the cochlea, fenestra rotunda, round window. (05 Mar 2000) |
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| fossula rotunda | A depression on the medial wall of the middle ear which has the fenestra cochleae (round window) in its lower portion. Synonym: fossula rotunda, little fossa of the cochlear window. (05 Mar 2000) |