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EAR

EAR. Outer Ear. Auricle: Layer of skin over cartilage framework. Lobule = fibrous fatty tissue with no cartilage. Sensory innervation: Great auricular nerve. Auriculotemporal nerve. Lesser occipital nerve. Outer Ear. External acoustic (auditory) meatus:

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EAR

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  1. EAR

  2. Outer Ear • Auricle: Layer of skin over cartilage framework. Lobule = fibrous fatty tissue with no cartilage. • Sensory innervation: Great auricular nerve. Auriculotemporal nerve. Lesser occipital nerve.

  3. Outer Ear • External acoustic (auditory) meatus: From auricle to tympanic membrane. 2.5 cm in length. S-shaped. Lined by skin and ceruminous glands.

  4. Middle Ear • Tympanic membrane: Dense fibrous membrane. Covered by skin externally. Covered by mucosa internally.

  5. Middle Ear • Tympanic cavity: Air-filled cavity within petrous portion of temporal bone. Round window: Enclosed by secondary tympanic membrane: Undergoes compensatory excursions with movement of stapes. Oval window: Closed by footplate of stapes.

  6. Middle Ear • Auditory ossicles: Malleus: Attached to tympanic membrane. Incus. Stapes: Attached to oval window (fenestra vestibuli).

  7. Middle Ear • Stapedius muscle: Inserts onto neck of stapes. Contracts reflexively in response to loud sounds. Innervated by CN VII.

  8. Middle Ear • Tensor tympani muscle: Inserts onto malleus. Contracts reflexively to loud sounds. Innervated by CN V-3.

  9. Middle Ear • CN IX: Tympanic nerve: GSA to mucosa of tympanic cavity, mastoid air cells, and auditory tube. Lateral petrosal nerve: Leaves tympanic cavity to floor of middle cranial fossa. Descends through foramen ovale to infratemporal fossa. Ends in otic ganglion.

  10. Inner Ear • Lies within petrous part of temporal bone. • Consists of: Bony labyrinth: Lined with periosteum. Membranous labyrinth. • Supplied by: Labyrinthine artery (from basilar artery): (Basilar artery is formed by fusion of two vertebral arteries).

  11. Inner Ear • Cochlea: Resembles a snail shell. Three turns. Round window (fenestra cochlea). • Vestibule: Contains: Utricle. Saccule.

  12. Inner Ear • Cochlear (auditory) nerve (CN VIII). • Semicircular canals: Anterior, posterior, lateral. Arranged in three planes. Open into utricle. Dilated at one end to form ampulla: With crista ampullaris. Senses rotational acceleration.

  13. Inner Ear • Utricle and saccule: With macula. Senses linear acceleration and pull of gravity. • Vestibular nerve (CN VIII):

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