Middle ear

1. Tympanic cavity
1. Anterior wall – eustacian tube opens into anterior wall. Connects nasopharynx w/ middle ear
1. Why this is good – equalizes pressure buildup, which could potentially rupture the tympanum
2. Why this is bad – it’s a communication. This means infection can spread b/w the two areas
2. Lateral wall – chorda tympani (CN VII) runs along lateral wall. Conveys taste from ant 2/3 of tongue and presynapic parasympathetics to submandibular ganglion
3. Posterior wall – communicates w/ mastoid air cells, which means middle ear infections can spread there. Difficult to treat!
4. Medial wall
1. Oval window – transmits vibration from stapes to the perilymph of scala vestibuli
2. Tympanic plexus – passes along tympanic bulla.
1. Carries sensory info from tympanum and external auditory meatus (CN’s IX and X).
2. Lesser superficial petrosal nerve – emerges from plexus. Carries p.p. of CN IX to otic ganglion
3. Round window – functions to dampen pressure waves transmitted to scala tympani

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