Anatomy of the Ear Divided into 3 major areas: outer, middle, inner



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Ear
Anatomy of the Ear

Divided into 3 major areas: outer, middle, inner

Outer and middle deal with hearing only

Inner deals with hearing and equilibrium

Outer or External Ear

Auricle (pinna): skin covered cartilage

Encircles the auditory canal opening

Lobule: inferior portion of the pinna

External Acoustic Meatus (external auditory canal): short, narrow

chamber


Opening in the temporal bone

Skin lines

Ceruminous Glands: wax secreting glands found in the walls of the

external acoustic meatus

Tympanic Membrane (eardrum): membrane that separates outer from

middle ear

Vibrates at the exact frequency as sound wave on it

Middle Ear: small chamber

Tympanic Cavity: another name for middle ear

Ossicles:

1. Malleus

2. Incus


3. Stapes

Form a lever system that amplifies and transmits vibrations of the

eardrum to the fluids of the inner ear

Pharyngotympanic Tube (auditory tube): connects the middle ear with the

nasopharynx

Is normally flattened and closed

Swallowing or yawning causes it to open temporarily to equalize

pressure of the middle ear

Otitis Media: inflammation of the middle ear

Fairly common condition in children and adults prone to sore

throats

If large amounts of fluid or pus accumulate, the eardrum may need



to be lanced to relieve pressure

Inner Ear (internal ear)

Osseous Labyrinth (bony labyrinth): bone chambers

3 subdivisions: cochlea, vestibule, semicircular canals

Perilymph: aqueous fluid that fills the osseous labyrinth

Membranous Labyrinth: suspended in the perilymph

Follows the contours of the osseous labyrinth

Endolymph: more viscous fluid that fills the membranous labyrinth

Vestibule and Semicircular Canals: involved with equilibrium
Cochlea: contains the sensory receptors for hearing

Cochlear Duct: winds through the cochlea

Separates the cochlear cavity into upper and lower chambers

Scala Vestibuli

Scala Tympani

Spiral Organ of Corti: contains the receptors for hearing called the sensory hair

cells

Cochlear Nerve: division of nerve VIII



Microscopic Anatomy of the Organ of Corti and the Mechanism of Hearing

Basilar Membrane: holds the hair cells

Tectorial Membrane: gelatinous membrane that lies over the hair cells

Vestibular Membrane: the roof of the cochlear duct

Scala Media: endolymph filled chamber of the cochlear duct

Presbycusis: a type of sensorineural deafness

Specifically, the inability to hear high tones or speech sounds

Caused by deterioration of the organ of Corti



Caused by aging or loud sounds


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