The eardrum, or tympanic membrane (TM), is the dividing structure between the outer and middle ear. Although it is an extremely thin membrane, the eardrum is made up of three layers to increase its strength.
The ossicles are the three tiny bones of the middle ear located directly behind the tympanic membrane. These are the three tiny bones (smallest in the human body) in the middle ear: malleus (hammer), incus (anvil,) and stapes (stirrup) and their job is to further amplify the sound. These three bones form a connected chain in the middle ear. The malleus is embedded in the innermost layer of the tympanic membrane, and the stapes is connected to a membranous window of the inner ear, called the oval window. The ossicles translate mechanical vibrations received at the eardrum into the inner ear.
The Eustachian tube is the middle ear’s air pressure equalizing system. The middle ear is encased in bone and does not associate with outside air except through the Eustachian tube. This tubular structure is normally closed, but it can be involuntarily opened by swallowing, yawning, or chewing. It can also be intentionally opened to equalize pressure in the ears, such as when flying in an airplane. When this happens, you might hear a soft popping sound.