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
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
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)
ventral expansion in horse---not sure about, maybe cools bld going from the body to the brain
*contains perilymph* vestibule---utricle & saccule; semicircular canals---comm. w/utricle; cochlea---scala vestibuli, scala tympani, modiolus, cochlear n, & spiral ganglion
What do you see when looking dn canal with an otoscope?
external & middle ear, never see internal!
*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
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
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 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
What responds best to high-frequency sounds?
narrow basilar memb. with greatest stiffness at the base
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 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)
The displacement of the otoliths is transmitted to the maculae via....
overlying gelatinous layer, causing bending of the stereocilia of the sensory cells
saccule & utricle
detect orientation of the head in a gravitational field & control posture, gait, equil.
Why are semicircular canals at right angles to one another?
to detect angular acceleration in any direction
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
change in head position (circ movement or angular acceleration) causes...
flow of endolymph in semicirc. ducts
movement of cilia...
is transduced into elect. impulses that're transmitted to brain via cr n 8
sound waves > air compression > deflection of basiclar membrane in cochlea > action potential