Ear Flashcards
What does the pharyngotympanic tube connect and what is its function?
Connects the middle ear to the nasopharynx. Allows for drainage from the middle ear into the pharynx and helps to equalise pressure (opens during swallowing).
What muscles control movement of the ossicles of the middle ear?
Tempor Tympani
Stapedius
How does the Tempor Tympani control oscillations in the ear?
Attaches to the neck of the malleus and pulls the tympanic membrane medially to reduce the force/ amplitude of vibrations
What nerve supplies the Tempor Tympani muscle?
CN Vc
How does the Stapedius control oscillations in the ear?
Pulls the stapes and limits its range of movement in response to large vibrations
What nerve supplies the Stapedius muscle?
CN VII
What is Hyperacusis?
Heightened sensitivity to certain noises caused by damage to CN VII (causing loss of innervation to the Stapedius muscle of the middle ear)
How can the Chorda Tympani be damaged and what does this result in?
Tympanic Membrane rupture can damage the Chorda Tympani resulting in a loss of taste sensation to the anterior 2/3 of the ipsilateral tongue
Where can middle ear infections spread to and what does this result in?
Mastoid air cells (mastoiditis) Facial nerve (ipsilateral facial palsy) Vestibular system (dizziness)
What is the clinical name for a middle ear infection?
Otitis Media
How does the ear develop embryologically?
From pharyngeal arches 1 and 2
How does the tympanic membrane develop embryologically?
From the ectoderm and endoderm of the 1st pouch and cleft
What is an auricular sinus?
An additional external auditory meatus that develops in front of your pinna (external ear)
Small and non-functional but can become infected or form a cyst
Within which bone is the inner ear located?
Petrous part of the temporal bone (between middle ear and internal acoustic meatus)
What is the nerve innervation to the inner ear?
CN VIII (Vesitbulocochlear) - enters via the IAM and divides into separate vestibular and cochlear branches
What is inflammation of the external auditory meatus called?
Otitis Externa (commonly called Swimmer’s Ear)
What is the sensory innervation of the external auditory meatus?
CN Vc and CN X
In which direction would you need to pull the pinna in order to examine the EAM?
Posteriorly + superiorly in adults
Posteriorly + inferiorly in children
[EAM is S-shaped and directed anteroinferiorly in adults]
What are the layers of the Tympanic Membrane and their sensory nerve innervation?
From lateral to medial:
Skin (CN Vc + X)
Mesoderm
Respiratory mucosa (CN IX)
Where could pain from the skin of the Tympanic Membrane refer to?
Mandible/ mandibular teeth Temporomandibular joint Laryngopharynx Larynx Cardiac
Where could pain from the respiratory mucosa of the Tympanic Membrane refer to?
Pharynx
What are the ossicles of the middle ear?
Malleus
Incus
Stapes
Within what bone is the middle ear located?
Temporal bone
What are the functions of the middle ear ossicles?
Amplify signals
Connect the tympanic membrane to the oval window (of the inner ear)
What does damage to the ossicles or middle ear disease cause?
Conductive hearing loss (opposed to sensorineural)
What is the consequence of blockage of the pharyngotympanic tube?
Prevents drainage of the middle ear (leading to blockage and infections)
Prevents pressure equalisation
What is acute infective otitis media?
Middle ear infection (usually caused by infection spread from nasopharynx)
Causes pus accumulation in middle ear leading to pain and swelling of the tympanic membrane (pain is often relieved if tympanic membrane bursts)
What is Chronic Secretory Otitis Media?
[Glue ear]
Caused by persistent build up of mucoid fluid due to blockage of the pharyngotympanic tube leading to conductive hearing loss
Can result in speech and language development problems in children
How do you test the cochlear portion of the inner ear clinically?
Tuning fork - Rinne + Weber tests
What is the Rinne test?
Tuning fork placed on mastoid until sound stops and then hold in the air by the EAM
Air conduction should be better than bone conduction
Rinne-negative (i.e. not able to hear when placed near EAM) = conductive deafness
What is the Weber test?
Tuning fork placed on forehead and ask patient where sound/ vibration is loudest and if it is louder on one side (lateralisation)
Normally should be no lateralisation
Conductive deafness = sound loudest in affected ear
Sensorineural deafness = sound loudest in normal ear
How can you tell which side you are looking at using the tympanic membrane?
Cone of light - points inferiorly and anteriorly
