Ear Anatomy Flashcards
Blood supply to the auricle (2)
Posterior auricular a.
Superficial temporal a.
Innervation of the auricle (4)
Great auricular n.
Auriculotemporal n.
Vagus n.
Facial n.
What is the course of the external acoustic meatus?
Extends from concha of auricle to tympanic membrane.
What part of the external acoustic meatus is bone vs. cartilage?
Lateral 1/3 is cartilage and slightly S-shaped.
Medial 2/3 is bone.
What is otitis externa (AKA Swimmer’s Ear)?
Fisk factors:
infection of external coustic meatus.
Excessive moisture, trauma, hearing aids, prior radiation, etc.
What is otitis media?
How does it look on exam?
Infection of middle ear (tympanic cavity).
Tympanic membrane is red and bulging.
Tympanostomy tube placement is done to do what?
Drain effusion behind tympanic membrane during OM.
Boundaries of the middle ear: roof, floor, lateral, medial, posterior and anterior walls.
Roof: tegmen tempani bone.
Floor: bone
Lateral: tympanic membrane
Medial: promontory, oval window, round window, facial canal.
Posterior: auditus to mastoid antrum, canal for facial n.
Anterior: opening of pharyngotympanic tube and canal for tensor tympani.
What does the bone of the floor separate the tympanic cavity from?
IJV
What does the anterior wall separate the tympanic cavity from?
ICA and sympathetic plexus
What does the tegmen tympani separate the tympanic cavity from?
Middle cranial fossa/temporal lobe
Contents of the middle ear (4)
Ossicles (malleus, incus, stapes)
Stapedius and tensor tympani ms.
Chorda tympani n.
Tympanic plexes
What does the head of the malleus articulate with?
What does the neck lie against?
Head of Incus.
Lies against flaccid part of tympanic membrane.
What is the handle of the malleus embedded in?
Where is the tip of it?
What muscle inserts at the handle?
Embedded in tympanic membrane.
Tip is at the umbo.
Tensor tympani m. inserts at handle.
What part of the incus articulates with the stapes?
The long limb of the incus
Head of stapes articulates with:
Neck of stapes is insertion site for:
Base (2 limbs) of stapes inserts on:
Incus.
Stapedius m.
Oval window.
Tensor tempani m. inserts on:
What does it do?
What is the end action?
Handle of malleus.
Pulls malleus medially –> tenses tympanic membrane.
Prevents damage from loud sound.
Stapedius m. inserts on:
What does it do?
What is the end action?
Neck of stapes.
Pulls stapes posteriorly and tilts it base in oval window.
Prevents damage from loud sound.
Chorda tempani n. is a branch of what?
What fibers does it have?
What is the function?
Branch of facial n.
PSNS fibers.
Taste to anterior 2/3 of tongue.
Tympanic n. is a branch of what?
What does it give rise to?
Glossopharyngeal n.
Tympanic plexus –> lesser petrosal n. (PSNS)
3 parts of bony labyrinth
Cochlea
Vestibule
Semicircular canals
Within which bone does the bony labyrinth sit?
What is it filled with?
Petrous part of temporal bone.
Perilymph.
What is the membranous labyrinth?
A series of communicating sacs and ducts suspended in bony labyrinth.
Parts of membranous labyrinth (3)
Vestibular labyrinth: utricle and saccule.
Semicircular ducts.
Cochlear labyrinth: cochlear duct.
What fills the membranous labyrinth?
Endolymph
