Clinically relevant anatomy of the ear Flashcards
Where are the organs of hearing & balance, facial nerve and vestibulocochlear nerve contained?
Petrous part of the temporal bone
Function of the middle ear?
Amplifies and conducts sound waves to the internal ear
Function of the external ear?
Collects and conveys sound waves to the tympanic membrane
Function of the internal ear?
Converts sensory information on sound/balance into FLUID WAVES and conducts the APs towards the brain stem
What is the internal ear?
The oval window to the internal acoustic meatus
What is the external ear?
From the auricle to the tympanic membrane
What is the middle ear?
From the tympanic membrane to the oval window
Nerve supply to the superior parts of the EAM & most of the tympanic membrane
CNV3
Nerve supply to the INFERIOR parts of the EAM & the tympanic membrane
CNX
Lymphatic drainage of the ear?
Parotid and mastoid nodes –>
Deep cervical nodes –>
Thoracic duct/right lymphatic duct –>
Right venous angle
(mastoid nodes = post-auricular nodes)
Where are the deep cervical nodes?
In the carotid sheath with the internal jugular vein
Tuning fork for ear
512Hz
Posteroinferiorly on tympanic membrane
Pars tensa
Anteroinferiorly on tympanic membrane
Light reflex
Most inwardly depressed part of the tympanic membane
Umbo
Nerve supply to middle ear cavity, eustachian tube, nasopharynx, oropharynx and the tonsils
CNIX
Nerve supply to middle ear cavity
CNIX
Nerve supply to eustachian tube
CNIX
Nerve supply to nasopharynx, oropharynx and tonsils
CNIX
Nerve supply to external surface of tympanic membrane
CNV3 (auriculotemporal branch)
Branch of V3 which supplies the external surface of the tympanic membrane?
Auriculotemporal branch
Nerve supply to the INTERNAL surface of the tympanic membrane?
CNIX
Doorway from mastoid antrum into the epitympanic recess
Aditus
Mastoiditis
Commonly due to spread of infection from middle ear cavity via the aditus
Which nerve passes through stylomastoid foramen and through internal acoustic meatus?
CNVII (facial nerve)
Nerve for balance
Vestibular (branch of CNVIII)
Nerve for hearing
Cochlear (branch of CNVIII)
Cupula
Apex of spiral (on cochlea)
Where is the membranous labryinth?
Within the bony labryinth
What is perilymph?
Fluid that fills the bony labryinth
membranous labryinth floats in perilymph and this is in the bony labryinth
Where do CNVII and CNVIII connect with the brainstem?
At the junctio nbetween the pons and medulla oblongata
Where does the chorda tympani supply?
Supplies the tastebuds of the anterior 2/3rds of the tongue
-parasympathetic supply to the submandibular and sublingual salivary glands
What does the tensor tympani do and which nerve is it supplied by?
Pulls on the handle of the malleus to tense the tympanic membrane
-supplied by CNV3
Smallest skeletal muscle in the body?
Stapedius
What does stapedius do?
Reduces stapes movement to protect the internal ear from excessive noise
(supplied by CNVII)
This canal connects the internal acoustic meatus to the stylomastoid foramen
Facial canal
Which nerve supplies the stapedius?
CNVII
The facial nerve’s base of skull course is through which bone?
Petrous temporal bone
Extracranial course of CNVII?
Enters the posterior aspect of the parotid salivary gland and then divides WITHIN the gland into somatic motor branches for muscles of facial expression
Muscle of the forehead
Frontalis (supplied by CNVII)
Sphincter of eyelid
Orbicularis oculi (supplied by CNVII)
Orbicularis oris
Sphincter of the lips
supplied by CNVII
How to clinically test CNVII?
Frown
Close eyes tightly
Smile
Puff out your cheeks