12 Functional Anatomy of the Ear Flashcards
What are the parts of the external ear lined with?
Skin
What is the middle ear filled with?
Air (fluid in middle ear= pathological)
What is the middle ear lined with?
Respiratory epithelium
What structure allows for equilibration of pressure in middle ear (air filled cavity) and drainage of mucus from middle ear?
Pharyngotympanic tube ( Eustachian tube) connects middle ear to oropharynx
Fill in the missing labels:
Which nerves carry general sensation from the ear ( touch, temperature, pain)? (implications for referred pain)
Branches of:
- V- Trigeminal
- Auriculotemporal
- VII- Facial (small contribution)
- IX- Glossopharyngeal
- Tympanic
- X- Vagus
- Cervical spinal nerves
Explain why nerves carrying general sensory information has implications for referred pain.
Pain/sensation felt in ear even if no pathology in ear
Eg in pharyngitis- ear pain even through no pathology of ear
Otalgia with normal ear examination- think alternative site of pathology
Give some examples of non-otological origins of otalgia. (general)
What makes up the external ear and what is its function?
Pinna, external auditory meatus and lateral surface of tympanic membrane
Function: collects, transmits and focuses sound waves onto tympanic membrane
What is Ramsey Hunt syndrome?
Viral- varicella zoster
Patient with facial nerve palsey and evidence of rash on external ear (may need to look in canal)
Shingles of facial nerve
What pathology is shown in this image:
Perichondritis
=inflammation of cartilage in pinna
(can be due to infection from ear piercing)
Why is it so important to recognise a pinna haematoma and treat it apporopriately?
Pericondrium- supplies blood to cartilage underneath
Haematoma- cuts off blood supply and may cause pressure necrosis
Ear will scar and alter shape of cartilage (califlower ear)
Where does the blood accumulate in a pinna haematoma?
Between cartilage and overlying pericondrium
Pericondrium- supplies blood to cartilage underneath
How is a pinna haematoma treated?
Drainage
Prevent re-accumulation of blood
Describe the structure of the external acoustic meatus (lining, composition, shape)
Composition:
Cartilaginous (outer 1/3)
Bony (inner 2/3)
Shape:
Sigmoid
Lining:
Keratinising, stratified squamous epithelium
Cartilaginous part: hair, sebaceous and ceruminous glands (produce ear wax)
Explain the self-cleaning function of the external acoustic meatus:
What is shown in the following image?
Normal otoscopic view of tympanic membrane
What is otitis externa? Give some causes of it
Inflammation of external ear
External auditory meatus-swollen- may afffect hearing
Causes:
Infective- pseudomonas aeriginosa
Eczema
What is malignant otitis externa?
(NOT cancerous but really bad- potentially life threatening)
Seen in immunocompromised patients
Infection of soft tissue of ear- starts to involve bone
Usually pseudomonas aeruginosa
What pathologies of the tympanic membrane are shown in the 2 images on the right?
Otitis media with effusion= glue ear- see flashcard 27
What is a cholesteatoma and what causes it? Why is it important to recognise?
A cholesteatoma is an abnormal, noncancerous skin growth that can develop in the middle section of your ear, behind the eardrum. It may be a birth defect, but it’s most commonly caused by repeated middle ear infections.
Name the 3 ossicles.
Connected by synovial joints
What do the ossicles do?
Function:
Amplify and relay vibrations from tympanic membrane to oval window in cochlea
Identify the 2 muscles that contract, if there is excessive vibration due to loud noise, in order to tamper ossicle movement.
Tensor tympani and stapedius
Otosclerosis is a common cause of hearing loss in young adults. How does it occur and what type of hearing loss does it cause?
How?
Ossicles fused at articulations due to abnormal bone growth (esp between base of plate of stapes and oval window of cochlea)
Exact cause unknown- environmental and genetic
Type of hearing loss?
Unilateral or bilateral conductive hearing loss
What is another name for otosclerosis?
otospongiosis
Otitis media (glue ear) with infusion is not due to infection but may predispose to infections. It is due to an eustachian tube dysfucntion. Explain how this can affect hearing.
Fluid and negative pressure in middle ear
Decreased mobility of ossicles and TM
How is ‘glue ear’ treated (usually problem in children)?
- Most resolve spontaneously- 2-3months
- If persistent: require gromets- equilibriate pressure with atmospheric pressure
What are the signs, symptoms and causes of an acute middle ear infection (acute ottitis media)?
How does the structure of the Eustachian tube differ between children and adults? Why is this significant?
What complications can occurr as a result of acute otitis media?
- Tympanic membrane perforation
- Facial nerve involvement
- Chorda tympani and nerve to stapedius run through middle ear cavity
- Mastoiditis (infection of mastoid bone)- requires IV antibiotics
- Intracranial
- Meningitis
- Sigmoid sinus thrombosis
- Brain abscess
Outline the route by which acute otitis media can cause mastoiditis.
Fill in the missing labels:
How do we perceive sound through the cochlear?
What symptoms (general terms) might a patient with inner ear pathology present with? (3)
- Hearing loss (sensorineural)
- Tinnitus
- Balance disturbances and vertigo
How does the vestibular apparatus work?
What are the 2 broad categories of hearing loss?
- Conductive hearing loss
- Sensorineural hearing loss
What is presbycusis?
Sensorineural hearing loss associated with old age
Bilateral and gradual
Outline the pathophysiology of benign paroxysmal postitional vertigo.
Little crystals- become dislodged in semicircular canals
Vertigo only (symptom)
Short lived episodes- seconds
What is Meniere’s disease?
Exact cause unknown
Differentiate between the infective conditions: acute labrynthitis and acute vestibular neronitis.
Give some possible causes for sensorineural and conductive hearing loss:
