Chapter 19: Diseases of the Eyes, Ears, Nose, and Throat

The normal middle ear is a cavity surrounded by bone on three sides and by a thin tissue membrane, the tympanic membrane, or eardrum on the fourth. Connected to the middle ear by a passageway is an air-filled honeycomb of bone called the mastoid cavity. Sound waves enter the outer ear, pass down the ear canal, and strike the eardrum. ................
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