Term
| what structures compose the external ear? |
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Definition
Auricle or pinna
External auditory meatus |
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Term
| what structures compose the middle ear? |
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Definition
Tympanic cavity
Epitympanic recess |
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Term
| what structures compose the inner ear? |
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Definition
Bony labyrinth
Membranous labyrinth |
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Term
| what is the auricle/pinna and what is it involved in? |
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Definition
Skin over a core of elastic cartilage.
Involved in sound localization and amplification. |
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Term
| the lateral 1/3 of the external auditory meatus is __________. |
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Definition
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Term
| the medial 2/3rd bone of the external auditory meatus is a part of which bone? |
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Definition
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Term
| what can be found on the lateral part of the external auditory meatus? |
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Definition
lined by skin with hairs, sebaceous glands and ceruminous glands (similar to apocrine sweat glands)
no eccrine sweat glands
cerumen is ear wax |
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Term
| which nerves innervate the external auditory meatus? |
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Definition
Mainly auriculotemporal nerve
Some small vagal branches (CN X)
Why some people gag when they clean their ears.
Minor innervation by facial nerve (VII)
External part of tympanic membrane
Auriculotemporal nerve |
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Term
| the auriculotemporal nerve is a branch of which nerve? |
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Definition
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Term
| what nerves innervate the outer and inner surface of the tympanic membrane? |
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Definition
Outer surface innervated mainly by the auriculotemporal nerve and small contribution by the auricular branch of the vagus nerve.
Inner surface is innervated by the glossopharyngeal nerve. |
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Term
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Definition
Bulging, red tympanic membrane may indicate middle ear infection.
More common in younger children because their pharyngotympanic tubes have a narrower angle and therefore, drainage from the middle ear cavity to the pharynx is impaired.
May cause perforation of tympanic membrane. |
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Term
| where is the incision made for treatment of otitis media? |
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Definition
Incision is made in the posteroinferior membrane to avoid injuring the chorda tympani and tympanostomy tube placed.
as it heals it pushes the tube out
have to be careful where you place it because if you injure chorda tympani you’ll cause loss of taste in 2/3rds of tongue and loss of innervation to submandibular and sublingual glands |
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Term
| the middle ear anteriorly connects to the pharynx via what structure? |
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Definition
| the pharyngotympanic tube (eustacian tube) |
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Term
| the middle ear posteriorly connects to mastoid cells via what structure? |
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Definition
mastoid antrum
mastoid antrum is a cavity in mastoid process of temporal bone, separated from middle cranial fossa by thin plate of temporal bone (tegmen tympani) |
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Term
| innervation of the middle ear cavity, including the inner surface of the tympanic cavity is by which nerve? |
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Definition
by tympanic nerve (CN IX)
tympanic nerve turns into plexus that gives off lesser petrosal nerve |
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Term
| what is the tensor tympani muscle and where is it attached? |
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Definition
Tensor tympani – attached to handle of malleus – tenses tympanic membrane and thereby attenuates sound
Innervated by trigeminal nerve, mandibular division V3 |
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Term
| what is the stapedius and where is it attached? |
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Definition
attaches to the neck of the stapes and thereby prevent excessive movement of the stapes
Innervated by facial nerve (CN VII)
Paralysis of the facial nerve can cause hyperacusis |
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Term
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Definition
| sensitivity to loud sounds |
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Term
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Definition
Otitis media can lead to mastoiditis, an inflammation of the mastoid antrum and air cells.
Mastoiditis can spread superiorly into the middle cranial cavity.
can spread and be a dangerous situation for children (bacterial meningitis) |
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Term
| describe the development embryologically of the ear |
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Definition
At 22 days of development there is a thickening of the surface ectoderm
otic placode invaginates to form otic or auditory vesicle
vesicle divides into two parts:
ventral component gives rise to the saccule and cochlear duct
dorsal component forms the utricle, semicircular ducts and endolymphatic duct |
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Term
| during development, the pharyngeal endoderm becomes which nerve? |
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Definition
| the glossopharyngeal nerve |
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Term
| the auditory ossicles form by which type of bone formation? |
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Definition
| endochondral bone formation |
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Term
| what are the 3 small bones which make up the ossicles? |
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Definition
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Term
| what is the embryonic origin of the malleus and the incus? |
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Definition
1st arch cartilage
Meckel's cartilage |
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Term
| what is the embryonic origin of the stapes? |
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Definition
2nd arch cartilage
Reichert cartilage |
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Term
| which nerve lies directly behind the handle of malleus in the tympanic membrane and may be damages by tubes placed in the tympanic membrane? |
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Definition
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Term
| what structures compose the bony labyrinth of the inner ear? |
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Definition
Within petrous portion of temporal bone
Made up of:
Semicircular canals
Vestibule
Cochlea
Contains perilymph |
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Term
| what structures compose the membranous labyrinth of the inner ear? |
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Definition
Made up of:
Cochlear duct
saccule
Utricle
Semicircular ducts
Endolymphatic duct
Contains endolymph |
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Term
| the otic placode forms from ______. |
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Definition
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Term
| what is the function of the vestibular apparatus? |
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Definition
The vestibular apparatus detects head position (linear acceleration) and head movement (angular acceleration).
It serves to orient us in 3-dimensional space.
It serves as a gyroscopic stabilizer for the visual system. |
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Term
| describe how hair cells are depolarized |
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Definition
when movement of endolymph travels and pushes stereocilia towards kinocilium, hair cells depolarize
embedded in gelatinous matrix that is pushed when endolymph moves, moves stereocilia in one direction
if it moves in opposite direction, stereocilia away from kinocilium, cell will hyperpolarize (right) |
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Term
| how is head position determined? |
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Definition
Linear acceleration (head position) is detected by specialized regions of neuroepithelial cells called maculae.
The maculae are located in the utricle and saccule.
The macula of the utricle is positioned in its lateral wall.
The macula of the saccule is positioned on its floor.
Therefore, the maculae are oriented perpendicular to one another.
The semicircular canals are set at right angles to each other and are oriented in three different planes.
They have specialized dilations, the ampullae which contain a ridge of neuroepithelial cells (hair cells) called the crista ampullaris.
Their cilia and stereocilia are embedded in a gelatinous matrix which forms a conical structure called the cupula.
The semicircular canals are responsible for detecting head movements (angular acceleration). |
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Term
| what are hair cells and where are they located? |
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Definition
Hair cells of the maculae have one cilium and an average of 60 long stereocilia.
These surface specializations are embedded in a gelatinous matrix. |
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Term
| what are otoliths and what is their function? |
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Definition
Embedded within the surface of the matrix are calcium carbonate crystals called otoliths.
Gravity causes the weight of the otoliths to distort the gelatinous matrix and thereby causes the receptor cells to fire.
crystals can get displaced and cause vertigo in people |
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Term
| what is meniere's disease? |
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Definition
Recurrent attacks of vertigo, hearing loss and tinnitus (ringing in ears).
May be accompanied by nystagmus
Most common in 4th and 5th decade.
Attacks may last for a few moments to a number of hours.
A consistent feature is endolymphatic hydrops, an increase in the volume of endolymph. |
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Term
| describe the auditory apparatus in general |
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Definition
Auditory apparatus captures and conducts sound.
Middle ear ossicles convert sound waves to fluid waves.
Fluid waves travel through perilymph.
Perilymph is not compressible and so transmits wave with relative fidelity. |
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Term
| the central core of the cochlea is a spiral bony structure called? |
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Definition
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Term
| what does the modiolus contain and where is it located? |
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Definition
The central core of the spiral of the cochlea is a bony structure the modiolus.
It contains the spiral ganglion and the acoustic portion of the vestibulocochlear nerve (CN VIII). |
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Term
| describe the cochlea and its divisions |
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Definition
Fluid wave travels through the cochlea from base to apex.
the cochlea is divided into three spaces:
scala vestibuli - above the cochlear duct
scala media = cochlear duct
scala tympani - below the cochlear duct
Scala vestibuli and tympani contain perilymph and are part of the bony labyrinth.
Scala media (cochlear duct) contains endolymph and is part of the membranous labyrinth. |
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Term
| what is found in the organ of corti and where is it located? |
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Definition
located in the scala media in the cochlea
important cells- hair cells (sensory, 3 rows of inner and one row of outer layer), and outer and inner pillar cells (very stiff, lots of microtubules in them, serves as fulcrum for movement of tectorial mb) |
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Term
| what is the function of the organ of corti? |
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Definition
Tonotopic deflection of basilar membrane causes it to move relative to the tectorial membrane.
The pillar cells are stiff because of their high content of microtubules and they act as a fulcrum for the movement of tectorial membrane.
The stereocilia of the outer and inner hair cells which are embedded in the tectorial membrane undergo sheer stresses that cause them to depolarize. |
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Term
| what are some causes of hearing loss? |
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Definition
Constant exposure to loud sounds at specific frequencies can damage hair cells that detect those frequencies
Hair cells in humans do not regenerate
Vestibulocochlear nerve may be injured at its entrance into the brainstem by a Schwann cell tumor, Schwannoma
Acoustic neuroma
May involve facial nerve and thereby cause facial paralysis |
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