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