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auricle (pinna)

auricular cartilage--elastic cart.; anular cartilage--attaches to osseous external auditory meatus

auditory meatus (external ear canal)

ceruminous glands (apocrine tubular sweat gl.) & sebaceous glands


(hairs) product of ceruminous glands, sebaceous gl., and sloughed cells

tympanic membrane (eardrum)

manubrium of malleus embedded here, separates external auditory canal from tympanic cavity

external /internal tympanic membrane epith

external-stratified squamous, internal-simple squamous; collagen fibers b/w, CT thicker where manubrium of malleus attaches; highly innervated/vascularized

tympanic cavity

simple squamous or cuboidal, air filled

auditory ossicles

connect tympanic memb. to memb. of vestibular (oval) window of inner ear; malleus, incus, stapes--smallest muscles in body

What inhibits damage to the cochlea by loud sound?

tensor tympani m. (malleus) and stapedius m. (stapes)

auditory (eustachian/pharyngotympanic) tube

communication with nasopharyns for pressure equalization (on plane, ears pop)

guttural pouch

ventral expansion in horse---not sure about, maybe cools bld going from the body to the brain

Where's inner ear?

in petrous part of temporal bone

bony labyrinth

*contains perilymph* vestibule---utricle & saccule; semicircular canals---comm. w/utricle; cochlea---scala vestibuli, scala tympani, modiolus, cochlear n, & spiral ganglion


axis of spongy bone; contains spiral ganglion, Cr nerve 8, bv

What do you see when looking dn canal with an otoscope?

external & middle ear, never see internal!

membranous labyrinth

*contains endolymph* utricle & saccule, 3 semicircular ducts, cochlear duct (scala media)


scala vestibuli (dorsal)--contains perilymph; cochlear duct (scala media)--contains endolymph + organ of Corti (spiral organ); scala tympani--contains perilymph


an opening at apex of cochlea that contains s. vestibuli and s. tympani

Where does s. tympani end?

cochlear (round) window

components of external ear

1) auricle/pinna, 2) external ear canal/auditory meatus, 3) tympanic membrane

components of middle ear

1) tympanic cavity, 2) auditory ossicles, 3) auditory (eustachian/pharyngotympanic) tube

components of inner ear

1) bony labyrinth, 2) membranous labyrinth

Where does s. vestibuli start and end?

oval window to apex of cochlea

What's the only lining epith. that's vascularized and what does it produce?

stria vascularis, endolymph

components of cochlear duct

1) tectorial membrane--vibrated by sound wave energy; 2) organ of Corti--hair cells (stereocilia), phalangeal cells (support), pillar cells (moved by sound wave energy and displace hair cells against a tectorial membrane); 3) basialar membrane---vibrated by sound wave energy, 4) stria vascularis--produces endolymph

components of cochlear apparatus

scala vestibuli, cochlear duct (scala media), scala tympani

components of organ of Corti

1) hair cells with stereocilia; 2) phalangeal cells (support); 3) pillar cells--moved by sound wave energy, displace hair cells against tectorial memb.

pathway of sound

outer ear---> tympanic memb > malleus, incus, stapes > vestibular window > scala vestibuli > helicotrema > scala tympani > deflects scala media > stimulates spiral ---> organ of Corti

4 steps--perception of sound

1) sound waves strike TYMPANIC MEMB. which transmits movement via MALLEUS, INCUS, STAPES to OVAL WINDOW of cochlea; 2) PERILYMPH movement causes VESTIBULAR MEMBRANE to move, causing movement of the BASILAR MEMBRANE; 3) PILLAR CELLS cause shearing action of hair cells against the TECTORIAL MEMB. impulses carried thru SPIRAL GANGLION to brain via CR N 8 and interpreted as sound; 4) sound wave energy is dissipated by bulging of the secondary tympanic memb. in the round window

How are sounds of different frequencies perceived?

resonance cords in basilar memb.

What responds best to high-frequency sounds?

narrow basilar memb. with greatest stiffness at the base

How is the impulse sent to the brain?

cranial nerve 8

3 organs of equilibrium and motion detection

1) utricle--determines orientation to gravity, 2) saccule--determines orientation to gravity, 3) semicircular ducts (3)--to deal with change in position

within organs of equil., 3 specialized structures that have neuroepithelial cells

1) macula utriculi--position of head & its linear movement, 2) macula sacculi--position of head & movement, 3) crista ampullaris--sensitive to angular acceleration/deceleration (MAJOR ORGAN)

Where is MACULA (region) of differentiated neuroepithelial cells?

vestibular apparatus--within thin sheet of CT lined with simple squamous epith & bound to periosteum of osseous labyrinth

What's macula innervated by?

branches of the vestibular n

What lies in the floor of the vest. app. and what lies on lateral wall?

macula of the saccule, macula of utricle (both perpendicular to each other--help determine if head is upright or on its side)

What's the vestibulocochlear nerve?

cr n 8

What shears the hair cells?

movement of otolithic memb

What displaces the otoliths in the saccule and utricle?

gravitational movement of the endolymph

The displacement of the otoliths is transmitted to the maculae via....

overlying gelatinous layer, causing bending of the stereocilia of the sensory cells

The electrical impulses generated are transmitted to the brain via

vestibulocochlear n (cr n 8)

saccule & utricle

detect orientation of the head in a gravitational field & control posture, gait, equil.

otoliths + gel=

statoconial memb

otoliths are part of...

statoconial (otolithic) memb

Why are semicircular canals at right angles to one another?

to detect angular acceleration in any direction

crista ampullaris

in the membranous ampulla of each duct (semicircular ducts); detects angular acceleration & deceleration--sensory epith composed of supporting cells & sensory hair cells which project into a cupula


gelatinous mass containing stereocilia & kinocilia in semicircular ducts

displacement of hair bundle stimulates...

hair cells in crista ampullaris of the semicircular ducts

change in head position (circ movement or angular acceleration) causes...

flow of endolymph in semicirc. ducts

endolymph movement displaces...

cupula of crista ampullaris, bending stereocilia on hair cells

movement of cilia...

is transduced into elect. impulses that're transmitted to brain via cr n 8

cochlear functions

sound waves > air compression > deflection of basiclar membrane in cochlea > action potential

vestibular functions

circular movement or angular acceleration > semicircular ducts; linear acceleration > otolithgs in maculae of saccule and utricle

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