EAR
Overview and Topographic Anatomy
Overview and Topographic Anatomy
GENERAL INFORMATION
Dual functions:
• Maintains the balance of the body (vestibular)
3 divisions:
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
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
Structures and Boundaries
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