Middle ear

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The Eustachian Tube: Structure, Function, and Role in the Middle EarThe correct Answer is a) eustachian tube orifice


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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