The Ear Flashcards
In which bone are the divisions of the ear found?
Temporal bone
What are the anatomic divisions of the ear?
External
Middle
Inner
What are the functional divisions of the ear?
Hearing (auditory system)
Balance (vestibular system)
What is the pterion?
H shaped suture
Joins frontal, parietal, temporal and sphenoid
Thinnest part of the skull
Which three processes are found in the temporal bone?
(Anterior to posterior)
Zygomatic process
Styloid process
Mastoid process
Which structure of the temporal bone prevents anterior dislocation of the TMJ?
Zygomatic process
Where is the stylomastoid foramen found and which structure exits here?
Between styloid process and mastoid process
Facial nerve
What are the two parts of the temporal bone?
Squamous (above EAM)
Petrous (rest of bone)
Where is the extra cranial opening into the carotid canal found?
Temporal bone
Which foramina are found in the anterior cranial fossa?
Cribriform plate of ethmoid bone
Which foramina are found in the middle cranial fossa?
Optic canal Superior orbital fissure Foramen rotundum Foramen ovale (Intracranial opening of carotid canal)
Which foramina are found in the posterior cranial fossa?
Internal acoustic meatus
Jugular formanen
Hypoglossal canal
(Foramen Magnum)
Which structures pass through the internal acoustic meatus?
CN VII - Facial Nerve
CN VIII - Vestibulocochlear Nerve
Labyrinthine artery (+ vein)
What are the functions of the Facial Nerve?
Motor to face Motor to stapedius Taste to ant 2/3rds of tongue Secretomotor to salivary glands and lacrimal gland General sensory to external ear
What are the functions of the Vestibulocochlear Nerve?
Balance
Hearing
What is the Labyrinthine artery?
Branch of anterior inferior cerebellar artery
From Circle of Willis
Which structures form the external ear?
Auricle to tympanic membrane vie external acoustic meatus
Which structures form the middle ear?
Tympanic membrane to oval window, including Eustachian tube
Which structures form the inner ear?
Oval window to internal acoustic meatus
What is the function of the external ear?
Collects and conveys sound waves to tympanic membrane
What is the function of the middle ear?
Amplifies and conducts found waves to the internal ear
What is the function of the internal ear?
Converts special sensory information into fluid waves, then APs and conducts APs to brain
Which are the components of the external ear “skeleton”?
Temporal bone
Elastic cartilage
(avascular, and so gets nutrients from the skin)
What are the components of the ear canal?
Begins at external acoustic meatus
Composed of 1/3 cartilage (elastic), 2/3 bony
Lined with skin
Produces earwax via ceruminous glands
What are the components of the auricle?
Helix Anti helix Concha Tragus Anti tragus Ear lobe
What is the innervation of the auricle?
C2,3 spinal nerves
CN VII - Facial nerve
Which parts of the external ear are supplied by CNV3?
Superior parts of EAM and most of the tympanic membrane (2/3)
Which parts of the external ear are supplied by CNX?
Inferior parts of EAM and tympanic membrane (1/3)
What is the lymphatic drainage of the auricle?
Lateral surface of superior half -> parotid lymph nodes
Cranial surface of superior half -> mastoid lymph nodes (and deep cervical)
Rest of auricle -> Superficial cervical lymph nodes
All eventually -> deep cervical lymph nodes
Then thoracic duct or right lymphatic duct at venous angles
Which direction should you pull the auricle for otoscopic examination in children?
Posteroinferiorly
EAM short and straight
Which direction should you pull the auricle for otoscopic examination in adults?
Posterosuperiorly
EAM is curved
Where is the cone of light normally seen in otoscopic examination, and why might this change?
Anteroinferiorly
Change of pressure within the middle ear
What is the general sensory nerve supply to the tympanic membrane?
External surface = mostly CN V3
Internal surface = CN IX
Which structures does the Glossopharyngeal Nerve provide sensory innervation to?
Middle ear cavity Eustachian tube Nasopharynx Oropharynx Tonsils
Which structures does the Eustachian tube connect?
Anterior wall of tympanic cavity to the lateral wall of the nasopharynx
Which three bones are contained in the middle ear?
Malleus
Incus
Stapes
Which two muscles are contained in the middle ear?
Stapedius
Tensor tympani
Branches from which cranial nerves are contained within the middle ear?
Facial nerve
Glossopharyngeal
By which joints do the auditory ossicles articulate?
Synovial joints
Which structure of the middle ear adheres to the internal aspect of the tympanic membrane, and what does this create?
Handle of the malleus
Creates the umbo (most inwardly depressed part of tympanic membrane)
Which structure in the middle ear fits into the oval window?
The base (footplate) of the stapes
What is the epitympanic recess?
Space superior to the tympanic membrane
Which nerve innervates tensor tympani muscle?
Mandibular division of trigeminal (CN V3)
What is the purpose of tensor tympani muscle?
Reduces the sound heard whilst eating
Where is the tympanic cavity found?
Petrous temporal bone
Which nerve passes the lateral wall of the tympanic cavity, over the tensor tympani muscle and past the tympanic membrane?
Chorda Tympani
What is the aditus?
Doorway into the mastoid antrum from the epitympanic recess
What causes mastoiditis?
Spread of infection from middle ear cavity
What are the implications of bacterial spread along the Eustachian tube?
Bacterial spread from pharynx/tonsils causing pain/hearing loss
What is the common nerve supply of the Eustachian tube and nasa/oropharynx and why is this clinically significant?
CN IX
Tonsillitis of pharyngitis can mimic earache
Common example of referred pain
What are the general functions of the facial nerve?
Special sensory
Sensory
Motor
Parasympathetic
What is the CNS connection of the facial nerve?
Brainstem, at ponotmedullary junction
What is the intracranial course of the facial nerve?
Directly into internal acoustic meatus in posterior cranial fossa
What is the base of skull foramen course of the facial nerve?
Temporal bone:
Internal acoustic meatus
Stylomastoid foramen
Which cranial nerve does Chorda tympani branch from?
CN VII (facial)
What are the functions of Chorda tympani?
Taste buds of the anterior 2/3 of the tongue
Parasympathetic supply to submandibular and sublingual salivary glands
What is the function of Stapedius?
Reduces stapes movement to protect the internal ear form excessive noise
What is the facial canal?
Connects the internal acoustic meatus to the stylomastoid process
Contains CNVII
Which nerve supplies stapedius?
CN VII
With which nerve does the Chorda tympani connect?
Lingual nerve branch of CN V3
What is the origin/attachment of the muscles of facial expression?
Originate = Bone Insert = Superficial fascia
What are the muscles of facial expression?
Frontalis
Orbicularis oculi
Elevators of lips
Orbicularis oris
How do you clinically test muscles of facial expression and motor function of CN VII?
Frown
Close eyes tightly
Smile
Maintain puffed out cheeks
Why is the buccal fat pad clinically significant?
Lost in illness, giving “sunken cheeks”
Clinical sign of malnutrition
What are the two components of the vestibulocochlear nerve?
Cochelar nerve - Hearing
Vestibular nerve - Balance
What is the otic capsule?
Dense bone capsule sitting within the temporal bone
Contains bony labyrinth
Explain the components of the otic capsule?
Membranous labyrinth containing endolymph fluid is suspended in perilymph fluid within the bony labyrinth
What is the physiological difference between perilymph and endolymph?
Perilymph = high K Endolymph = low K
How many turns does the cochlea undergo?
2.5
How are the semi-circular canals named?
Superior
Lateral
Posterior
What is the cochlear duct?
Long balloon like structure within the cochlea filled with endolymph
Through which nerve are APs from the cochlear duct conducted to the brainstem?
Cochlear nerve
What are the semicircular ducts?
Interlinked balloon like structures within the semicircular canals filled with endolymph
Through which nerve are APs from the semicircular ducts conducted to the brainstem?
Vestibular nerve
Which movement do the semicircular ducts detect?
Angular movement change
Which movement do the urticle and saccule detect?
Linear movement change
U = Horizontal
S = Vertical
How does the vestibular apparatus detect movement change?
Hair cells are stimulated by the movement of endolymph
What is are maculae?
Regions of the internal ear where clusters of hair cells are found
Describe sound transmission to the internal ear?
Sound waves make tympanic membrane vibrate
Vibrations transmitted through ossicles
Base of stapes vibrates in oval window
Creates pressure was in perilymph
Hair cells in cochlea move, APs stimulated and conveyed to brain by cochlear nerve
Pressure waves descend and become vibrations again
Pressure waves dampened at round window
Where in the cochlear apparatus are auditory stimuli detected?
Receptor cells in the organ of Corti
Located on the basil membrane of cochlear duct
What are the two parts of the cochlear canal?
Scala vestibuli
Scala tympani
What is the course of the vestibulocochlear nerve?
CNS at pontomedullary junction
Internal acoustic meatus
Divides to cochlear nerve axons -> cochlea
and vestibular nerve axons -> semicircular ducts
