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63 terms

EAR ANATOMY

STUDY
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Parotid Gland
Lies anterior to the ear between masseter muscle and skin. Opens to the stensen's duct.
Submandibular Gland
Lies along medial aspect of mandibular body. Opens to the Wharton's ducts.
Auricle
Consists chiefly of cartilage and has a firm elastic consistency. External ear.
Helix
Prominent outer ridge of auricle
Antihelix
Inner ridge of auricle
Tragus
The ear canal opens behind the _________.
Lobule
Fleshy projection of the earlobe
External Acoustic Meatus
Short curved tube (about 24mm long by 0.6cm wide) that extends from auricle to TM.
Ceruminous glands
Glands in the skin of the ear canal
Tympanic membrane
Contains outer cutaneous layer, intermediate fibrous layer, and inner mucous layer. Boundary between outer and middle ear.
Pars Flaccida
Above the short process of malleus bone. small portion of TM
Umbo
where the eardrum meets the tip of the malleus
Membranous labrinyth
continuous series of membranous sacs and ducts contained within the labyrinth.
endolymph
interior of Membranous labrinyth
Utricle and saccule
house equilibrium receptor regions called maculae
semicircular ducts
communicates with the utricle anteriorly
cochlear duct
houses the spiral organ of corti (the receptor organ for hearing)
Epitympanic recess
"roof" of the middle ear cavity
auditory tube
links the middle ear with nasopharynx
tympanic cavity
small air filled mucosa lined cavity in the petrous portion of the temporal bone
perilymph
fills bony labyrinth. fluid similar to CSF

The fluid in the space between the membranous and bony labyrinths of the inner ear, resembles extracellular fluid in composition (sodium salts are the predominate positive electrolyte)
vestibule
central egg shaped cavity of the bony labyrinth

the central part of the osseous labyrinth, and is situated medial to the tympanic cavity, behind the cochlea, and in front of the semicircular canals, it contains the utricle & saccule and is involved in balance
cochlea
spiral, conical bony chamber about the size of a split pea

Coiled resembles a snail shell, it contains the organ of Corti that's responsible for hearing. It consists of the scala vestibule (upper passageway which begins in the vestibule and receives the vibrations transmitted to the perilymph at the oval window), the scala tympani (lower passageway), and cochlear duct (auditory portion). The base of cochlea joins adjoins the vestibule
External Ear
gathers sound energy and focuses it on the eardrum
Auricle
fleshy part of the external ear on the external ear on the outside of the head; consists mainly of elastic cartilage covered w/ skin. Its shape helps collect sound waves & direct them toward the external acoustic meatus
External acoustic (auditory) meatus
Opening of ear leading to TM. Leads inward from the bottom of the auricula and conducts the vibrations to the tympanic cavity
External acoustic (auditory) canal
passageway that leads from the outside of the head to the tympanic membrane. The outside third of the canal wall consists of cartilage, and the inner two-thirds of the wall are made of bone. Canal is nearly 1 inch (2.5 cm) in length and is lined with skin that extends to cover the tympanic membrane. Tiny hairs directed outward and modified sweat glands that produce cerumen (earwax) help to discourage insects from entering the ear.
Lateral segment
external one third of canal, formed by cartilage; wider than the bony portion and has numerous ceruminous glands that produce earwax.
Ceruminous glands
produce earwax-prevents foreign objects from reaching delicate eardrum
Medial segment
internal two thirds of canal, formed by bone
Tympanic membrane:
thin semi-transparent, nearly oval, 3 layered membrane separates external ear from middle ear. Function is to transmit sound from the air to the ossicles inside the middle ear, and then to the oval window in the fluid-filled cochlea. well-supplied with blood vessels, and its sensory nerve fibers make it extremely sensitive to pain.
Outer cutaneous layer
continuous with the skin on the external canal
Intermediate fibrous layer
gives the membrane its tension and stiffness
Inner mucous layer
continuous with the mucous membrane lining the middle ear
Pars flaccida
the small, triangular portion of the tympanic membrane lying between the lateral process of the malleus and the margins of the tympanic incisure
Pars tensa
the drumlike part of the tympanic membrane
Umbo
small projection at the center of the outer surface of the eardrum; where eardrum meets the tip of the malleus
membranous labyrinth
The fluid-filled membranous sacs of the inner ear that are associated with the senses of hearing and balance
Endolymph
clear fluid that fills labyrinth
Utricle
oval shaped, larger of 2 sacs of vestibular labyrinth in inner ear. Communicates w/ semicircular ducts, the saccule, & endolympatc duct, all of which are filled w endolymph. In its wall is a sensory area w/hair cells that respond to movement of otoliths as the position of the head
inner ear
Consists of bony labyrinth & membranous labyrinth, located deep w/in temporal bone behind eye socket. 3 parts are cochlea, vestibule, & semicircular canals. the place where vibrations are transduced to specific nerve impulses that are transmitted through the acoustic nerve to the central nervous system (CNS).
acoustic apparatus
the cochlea housing the cochlear duct for auditory sense, and the vestibular apparatus , the vestibule housing the utricle and saccule, and the semicircular canals housing the semicircular ducts for the sense of equilibrium.
Semicircular canals
Kinetic labyrinth, 3 canals-at right angles to one another (the horizontal semicircular canal (also known as the lateral semicircular canal),superior semicircular canal (also known as the anterior semicircular canal), and the posterior semicircular canal) and their dilated ends are called ampullae , which detect rotational or angular acceleration. Together functioning in maintenance of the sense of balance in the body.
scala tympani
Duct filled w/ perilymph that's below the organ of Corti. It extends from the round window to the tip of the tip of the cochlea; communicates with the scala vestibuli through the helicotrema at the apex of the cochlea and ends at the round window, where the sound pressure waves are dissipated
Organ of Corti
A specialized structure located on the inner surface of the basilar membrane of the cochlea containing hair cells that transmit sound vibrations to the nerve fibers.
Cochlear duct (scala media)
is an endolymph filled cavity inside the cochlea, is wedged between the scala vestibuli and scala tympani and contains endolymph and the spiral organ of Corti , with receptor cells (hair cells) for auditory stimuli (the sense of hearing).
Saccule
smaller than utricle, communicates w utricle, cochlear duct, and endolymphatic duct, all filled w endolymph. In sensory area of its wall small hair cells respond to gravity or bodily movements
Utricle
oval shaped, larger of 2 sacs of vestibular labyrinth in inner ear. Communicates w/ semicircular ducts, the saccule, & endolympatc duct, all of which are filled w endolymph. In its wall is a sensory area w/hair cells that respond to movement of otoliths as the position of the head changes.
membranous labyrinth
The fluid-filled membranous sacs of the inner ear that are associated with the senses of hearing and balance.
Middle ear
Consists of the tympanic cavity with its ossicles and is located within the petrous portion of the temporal bone. Transmits the sound waves from air to auditory ossicles and then to the inner ear.
Tympanic cavity
small air-filled, mucosa-lined cavity within the temporal bone. Flanked laterally by the eardrum and medially by a bony wall with the oval and round windows Includes the tympanic cavity proper (the space internal to the tympanic membrane) and the epitympanic recess. Communicates anteriorly with the nasopharynx via the auditory (eustachian) tube and posteriorly with the mastoid air cells and the mastoid antrum through the aditus and antrum.
Is traversed by the chorda tympani and lesser petrosal nerve.
Epitympanic recess
the upper part of the tympanic cavity, above the level of the tympanic membrane, containing part of the incus and malleus.
Auditory tube
Connects the middle ear to the nasopharynx. Allows air to enter or leave the middle ear cavity and thus balances the pressure in the middle ear with atmospheric pressure, allowing free movement of the tympanic membrane. Has cartilaginous portion that remains closed except during swallowing or yawning. Is opened by the simultaneous contraction of the tensor veli palatini and salpingopharyngeus muscles
Mastoid air cells
air cells of various sizes and shapes in the mastoid process of the temporal bone
Oval window
(or vestibular window) is a membrane-covered opening which leads from the middle ear to the vestibule of the inner ear. Its' pushed back and forth by the footplate of the stapes and transmits the sonic vibrations of the ossicles into the perilymph of the scala vestibuli in the inner ear.
Round window
1 of two openings into the inner ear, situated below & a little behind the oval window; allows fluid in the cochlea to move, which in turn ensures that hair cells of the basilar membrane will be stimulated and that audition will occur. Is closed by the secondary tympanic (mucous) membrane of the middle ear and accommodates the pressure waves transmitted to the perilymph of the scala tympani.
Tensor tympani
MUSCLE

Arises from the cartilaginous portion of the auditory tube.
Inserts on the handle (manubrium) of the malleus.
Is innervated by the mandibular branch of the trigeminal nerve.
Draws the tympanic membrane medially and tightens it (in response to loud noises), thereby increasing the tension and reducing the vibration of the tympanic membrane.
Stapedius
MUSCLE

Is the smallest of the skeletal muscles in the human body.
Arises from the pyramidal eminence, and its tendon emerges from the eminence.
Inserts on the neck of the stapes.
Is innervated by a branch of the facial nerve.
Pulls the head of the stapes posteriorly, thereby tilting the base of the stapes.
Prevents (or reduces) excessive oscillation of the stapes and thus protects the inner ear from injury from a loud noise.
Its paralysis results in hyperacusis.
1. Protection
2. Selective attenuation of low frequency
Functions of middle ear muscle reflex:
1. _______ of inner ear from damage due to excess noise
2. __________ of ______ frequency sounds emitted from normal body mechanisms like flowing of blood through vessels etc by these muscles have been shown to improve the intelligibility of speech
Ossicles
3 bones Malleus, Incus, & Stapes; transmit sounds from the air to the fluid-filled labyrinth (cochlea). The absence of the auditory ossicles would constitute a moderate-to-severe hearing loss.
Malleus (hammer)
Consists of a head, neck, handle (manubrium), and anterior and lateral processes.
Its rounded head articulates with the incus in the epitympanic recess.
Its handle is fused to the medial surface of the tympanic membrane and serves as an attachment for the tensor tympani muscle
Incus (anvil)
Consists of a body and two processes (crura).
Its long process descends vertically, parallel to the handle of the malleus, and articulates with the stapes.
Its short process extends horizontally backward to the fossa of the incus and provides the attachment for the posterior ligament of the incus.
Stapes (stirrup)
Consists of a head and neck, two processes (crura), and a base (footplate).
Its neck provides insertion of the stapedius muscle.
Has a hole through which the stapedial artery is transmitted in the embryo; this hole is obturated by a thin membrane in the adult.
Its base (footplate) is attached by the annular ligament to the margin of the oval window (fenestra vestibuli). Abnormal ossification between the footplate and the oval window (otosclerosis ) limits the movement of the stapes, causing deafness.