Session 6 - Ear anatomy Flashcards
What are the three main parts of the ear?
The external, middle and internal ear.
What is the main, visible part of the external ear?
The auricle
What are the three main features of the external ear?
The helix
The tragus
The lobule
What is the blood supply to the external ear?
The posterior aurcular and superficial temporal arteries, which are both branches of the external carotid artery
What is the sensory innervation anterior to the external acoustic meatus?
Auriculotemporal nerve, a branch of the mandibular nerve
What is the sensory innervation of auricle behind the EAM
Great auricular nerve
Outline the structure of the EAM canal
Cartaliginous tube for the lateral 1/3rd, bony canal for the medial 2/3rds
Where does EAM lie?
In the temporal bone
What is the gooey stuff in ears?
Cerumen, which mixes with dead skin cells to form wax
What is the best way to view the EAM in adults?
Pull the ear upwards and backwards
What is the best way to view the EAM in children?
Auricle is pulled downwards and backwards
What can be visualised through the tympanic membrane?
The malleus
What is the external surface of the tympanic membrane innervated by?
Auriculotemporal nerve branch of CN V3
Auricular branch of the vagus nerve CN X
What is the internal surface of the tympanic membrane supplies by?
The glossopharyngeal nerve
What is Arnold’s cough reflex?
Stimulation of the auricular branch of the vagus nerve, by touching the tympanic membrane with a cotton bud, can cause cough/vomiting
What is wrong with the tympanic membrane if you can see dense white plaques?
Tympanosclerosis
What does bulging of the tympanic membrane mean?
Pus or fluid in middle ear (otitis media)
What would a retracted tympanic membrane demonstrate?
Infratympanic cavity pressures reduced due to obstruction of eustachian tube
What is found in the middle ear?
Auditory ossicles - Malleus - Incus - Stapes Stapedius and tensor tympani msucles Chorda tympani nerve Tympanic plexus of nerves
What are the two parts of the cavity of the middle ear?
Tympanic cavity proper
Epitympanic recess
What is found in the tympanic cavity proper?
Connected anteromedially with the nasopharynx by the eustachian tube
Connected posterolaterally with the mastoid air cells through the mastoid antrum
What is the tympanic cavity lined by and what is it continius with?
Mucous membrane, continous with lining of the pharyngotympanic tube, mastoid air cells and mastorid antrum
When is the mastoid antrum open?
During swallowing, thanks to the action of the palate muscles
What is the porpoise of the ossicles?
Relay the vibrations encountered by the tympanic membrane to the internal ear, amplifying and concentrating sound energy to the oval window
What are the two parts of the malleus?
Handle is attached to the tympanic membrane
Body articulates with the body of the incus
What does the incus articulate with?
The stapes
What does the stapes articulate with?
THE BONY LABYRINTH OF THE INNER EAR AT THE OVAL WINDOW
No need to shout :(
Outline the location and role of the tensor tympani
o Inserts into the handle of the malleus
Pulls handle medially
Tenses the tympanic membrane, reducing the amplitude of its oscillations
o Prevents damage to the inner ear when exposed to loud sounds
Outline the location and role of the stapedius
o Pulls the stapes posteriorly and tilts its base in the oval window
Tightens the anular ligament and reduces the oscillatory range
o Prevents excessive movement of the stapes
o Nerve to Stapedius arises from the Facial Nerve (CN VII)
What is the most important anatomical relationhsip of the middle ear?
The facial nerve, which lies in the facial canal separated from the tympanic cavity by a very thin bony partition
Where is the inner ear found?
In the petrous temporal bone. This bone forms bony labyrinth, surrounding the membranous labyrinth
What five structures does the inner ear contain?
Vestibule Semi-circular ducts and canals Choclea Cochlear duct Organ of corti
What is the vestibule of the inner ear?
Small bony chamber, containing the Utricle and Saccule, which are sensitive to rotational acceleration and the static pull of gravity
What is the semi-circular ducts and canals?
Communicate with the vestibule
Contain receptors that respond to Rotational Acceleration in three different planes
What is the cochlea?
Shell shaped portion of the bony labyrinth containing the Cochlear Duct
What is the cochlear duct?
Accommodates the spiral Organ of Corti
What is the organ of corti?
Contains the receptors of the auditory apparatus
