Hypotympanum

The hypotympanum refers to the portion of the tympanic cavity lying inferior to the level of the inferior margin of the external acoustic canal (EAC).

Gross anatomy

The hypotympanum is the smallest of the three compartments that make up the tympanic cavity and is a shallow depression in the floor of the middle ear. It is separated from the mesotympanum by an axial plane drawn between the inferior cochlear promontory and the tympanic annulus. Anteriorly is the opening into the Eustachian tube which passes anteromedially to the nasopharynx.