GA: Ear Flashcards
(32 cards)
What are the 3 general divisions of the ear?
Inner ear: auricle (pinna) + external acoustic meatus (ear canal)
Middle ear: Tympanic cavity + epitympanic recess (ossicles: malleus, incus, stapes + chorda tympani N. + tympanic plexus)
Internal Ear: Vestibulocochlear organ (hearing _ balance)
Parts of Auricle
What is the blood supply for the auricle (& pinna)?
Posterior Auricular + Superficial Temporal A.’s
(from ECA)
What is the innervation for the auricle?
Great auricular N.
Auriculotemporal N.
Vagus N.
Facial N.
What causes an auricular hematoma?
Trauma to ear –> causes blood to build up between perichondrium + cartilage
If not drained, fibrous tissue can form and this can cause califlower ear
What does the external acoustic meatus consist of?
lateral 1/3 = cartilage
medical 1/3 = bone
Which way do you pull an ear during an exam?
Posterior, Superior, and slightly lateral
What is otitis externa?
“swimmers ear”
Infection of external acoustic meatus
Risk factors: excessive moisture (pool), trauma (cleaning), anything the covers ear canal (earphones)
What is the purpose of the tympanic membrane?
It separates the external acoustic meatus from the middle ear.
Reflects cone of light
Where are the incus + malleus heads found?
In the epitympanic recess of
Which “portion” is the cone of light in?
Anterior and Inferior
What is otitis media?
Infection of the middle ear
Causes swelling of tympanic membrane and can block pharyngotympanic tube (eustacian tube)
Describe the steps taken in treatment of chronic middle ear infections (i.e. myringotomy and tympanostomy).
You would place a tympanostomy tube.
myringotomy –> incision to open eardrum
tympanostomy –> tube placed for continual drainage
What is the middle ear cavity roof boundry?
Tegmen tympani bone
Separates tympanic cavity from middle cranial fossa (temporal bone & brain)
Infection here can cause meningtitis
What is the middle ear cavity floor boundry?
bone
Separates tympanic cavity from the bulb of the internal jugular V.
What is the middle ear lateral boundry?
Tympanic membrane
Separates tympanic membrane from external ear
What is the middle ear medial boundry?
Promontory (formed by cochlea), oval window, round window, and prominence of facial canal
Separates the tympanic cavity from the inner ear
What is the middle ear posterior boundry?
Aditus to mastoid antrum, canal for facial nerve
Separates tympanic cavity from mastoid air cells + facial canal
What is the anterior wall middle ear boundry?
Opening of pharyngotympanic tube + canal for tensor tympani
Separates tympanic cavity from Carotid
*If infection errodes through anterior wall you can hit carotid*
What are the components of the middle ear?
Ossicles (malleus (tip = umbo), incus, stapes) MIS
Stapedius + tenso tympani M.’s
Chorda tympani N.
Tympanic plexus
What is the function + innervation of the tensor tympani muscles in the middle ear?
Help dampen loud sounds.
It inserts on mallelus and pulls it medially, and tenses the tympanic membrane so vibrations can’t move as well. This action prevents hearing damage from loud sounds.
Innervated by CN V3
What is the function + innervation of the stapedius M.?
Inserts on stapes
Prevents damage from loud sounds
CN VII
The facial nerve gives off ________ and carries parasympathetic fibers to preform __________.
Chorda tympani
Taste on anterior 2/3 of tongue
The glossopharyngeal N. gives off _______ which gives rise to the parasympathetic ________ N.
Tympanic plexus
Lesser petrosal N. –> innervates parotid
