18: Ear

CHAPTER 18

EAR

Overview and Topographic Anatomy

Structures and Boundaries

Muscles

Nerve Supply

Vascular Supply

Clinical Correlates

Questions

Overview and Topographic Anatomy

GENERAL INFORMATION

Dual functions:

Maintains the balance of the body (vestibular)

Perceives sound (auditory)

3 divisions:

external ear

middle ear

inner ear

External Ear

The most superficial portion of the ear, the external ear includes the auricle, external acoustic meatus, and the tympanic membrane

Helps gather sound and direct it to the tympanic membrane

Middle Ear

Transmits sound vibrations from the tympanic membrane to the inner ear via the ear ossicles: malleus, incus, and stapes

Mainly within the petrous portion of the temporal bone

General shape resembles a biconcave lens

Composed of the tympanic cavity that connects anteriorly with the nasopharynx via the auditory tube and the mastoid air cells posteriorly

Tympanic cavity contains the ear ossicles (malleus, incus, and stapes), muscles (tensor tympani and stapedius muscles), nerves (chorda tympani, tympanic branch of the glossopharyngeal nerve, and lesser petrosal nerve), and tympanic plexus (parasympathetics from the glosspharyngeal nerve plus sympathetics from the superior cervical ganglion via the carotid plexus)

Inner Ear

Vestibular and auditory structures, which are filled with fluid, make up the inner ear:

Auditory portion (cochlea) is stimulated by the movement of the fluid

Vestibular portion (utricle, saccule, and semicircular canals) is stimulated by fluid movement within these chambers

Consists of a membranous labyrinth that lies within an osseous labyrinth

The receptors for auditory and vestibular function are located within the membranous labyrinth

Fluids located in the membranous labyrinth (endolymph) and osseous labyrinth (perilymph) stimulate the auditory and vestibular receptors

The vestibulocochlear nerve enters the internal ear via the internal acoustic meatus

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Structures and Boundaries

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Jan 5, 2015 | Posted by in General Dentistry | Comments Off on 18: Ear
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