Middle Ear: Cavity and Contents
The middle ear (tympanic cavity) is an air-filled space in the temporal bone that houses the auditory ossicles and translates sound waves from the external environment into fluid vibrations in the inner ear.
| Structure | Key Functional Details |
|---|---|
| Auditory Ossicles | Malleus, Incus, Stapes. These bones amplify sound. |
| Stapedius Muscle | Innervated by CN VII. Dampens stapes movement to protect the inner ear from loud noise. |
| Tensor Tympani | Innervated by CN V3. Tenses the tympanic membrane. |
High-Yield Clinical Notes:
- Eustachian Tube: Connects the middle ear to the nasopharynx; equalizes pressure. In children, it is shorter and more horizontal, predisposing them to otitis media.
- Chorda Tympani: A branch of CN VII that runs across the middle ear space; often vulnerable during ear surgery, leading to taste disturbance (anterior 2/3 of tongue).
- Hyperacusis: Paralysis of the stapedius muscle (often due to CN VII palsy) results in increased sensitivity to everyday sounds.