7.1 Anatomy Of The Ear - need to write part3+4 Flashcards
What are the 2 functions of the ear?
Hearing
Balance
What are the 3 broad regions of the ear?
External
Middle
Inner
What is Otalgia?
Ear pain
What are signs and symptoms associated with ear disease?
Otalgia Discharge Hearing loss Tinnitus Vertigo Facial nerve palsy
What is tinnitus?
Perception of hearing sound without any external source for it
What is vertigo?
Sense of the world rotating around despite being still
Hallucination of movement
Why might patients with ear disease suffer facial nerve palsy?
As the facial nerve runs through the petrous bone, in close proximity to the middle ear.
What are the structures of the external ear?
Pinnacle
External auditory meatus
Skin lined cavity up to lateral surface of the tympanic membrane
What are the structures of the middle ear
Air filler cavity
Ossicles
Lined with respiratory epithelium
Pharyngotympanic tube
What is the boundary between structures of he external ear and structures of the middle ear?
The tympanic membrane
What is the intermittent connection from the middle ear to the nasopharynx called?
The Pharyngotympanic tube
Why is the connection between the middle ear and the nasopharynx intermittent?
Because the pharyngotympanic tube is a muscular tube that can intermittently close/open to equilibrate with atmospheric pressure within the nasopharynx
What are the 3 ossicles in the middle ear cavity?
Masseus
Incus
Stapes
What is the structure of the respiratory epithelia?
Pseudostratified columnar ciliates epithelium with goblet cells.
What are the structures of the inner ear?
Cochlea
Semicircular canals
(Both fluid filled)
What is the function of the cochlear?
To generate APs to send to the brain to receive sound
Describe the structure of the semicircular canals?
3 fluid filled semicircular structures at 90 degrees to each other
What is the function of the semicircular canals?
To generate APs that are sent to the brain to be perceived as our sense of position and balance
Why is referred Otalgia so common?
As many different nerves carry general sensation from the ear
What nerves carry GENERAL sensation from the ear?
Cervical spinal nerves (C2/C3) Vagus Trigeminal (auriculotemporal n.) Glossopharyngeal (tympanic n.) Facial nerve
What nerves carry the special sensation of hearing and balance from the ear?
Vestibulococchlear nerve ( CN XIII)
Where does the auriculotemporal nerve carry general sensory information from?
Lateral surface of the tympanic membrane
External acoustic meatus
Temporomandibular joint.
Why might pathology in the pharynx/larynx be felt in the ear?
Pain may be misinterpreted by the brain and referred to the ear as both are supplied by the glossopharyngeal nerve
What are potential non-otological causes for Otalgia?
TMJ dysfunction
Diseases of oropharynx
Disease of larynx and pharynx including cancers
How keep is the external auditory meatus in an adult?
2.5cm
What is the function of the external ear?
Collecting, transmitting, funnelling, focusing vibrations onto the tympanic membrane
What happens to the tympanic membrane when we hear sounds?
The tympanic membrane vibrates
What is the auricle composed of?
Cartilage, skin and fatty tissue (lobules)
What injuries are the auricle prone to?
Congenital
Inflammatory
Infective
Traumatic
Why is the auricle sometimes affected in facial nerve palsy?
Ramsey Hunt Syndrome. Reactivation of varicella zoster virus in the facial nerve. Auricle may present as red, painful with vesicles
What is perichondritis?
Infection of the perichondrium.
What is the perichondrium?
The perichondrium is connective tissue that overlies the cartilage of the pinna. Supplies blood supply to the pinna cartilage
What causes perichondritis?
Ear piercings
Insect bites
Anything that can cause infection of the skin of the ear
What is a pinna Haematoma?
Accumulation of blood between the cartilage and its overlying perichondrium from blunt injury
When do subperichondrial Haematomas occur?
During blunt force trauma - contact sports
What complication can happen due to a subperichondrial haematoma?
Strips the perichondrium from the cartilage. Cartilage is stripped from its blood supply as cartilage is avascular.
Accumulation of blood causes increase in pressure. Pressure pushes against cartilage and causes tissue necrosis
How are pinna Haematomas treated?
Drainage, aspirating the blood. This allows re-apposition of the perichondrium over the cartilage. Prevent re-accumulation by applying a tamponade to keep the pareichondrium against the cartilage
What occurs if a pinna Haematoma is not treated?
Cartilage becomes ischaemic as no blood supply. Scarring and fibrosis occurs. Cartilage develops asymmetrically resulting in cauliflower deformity to the ear
Describe the epithelium on the external acoustic meatus
Keratinising, stratified squamous epithelium
What is the embryological origin of the external acoustic meatus?
clefts between the 1st and second pharyngeal arches lined with ectoderm
Describe the structure of the external auditory meatus?
Outer cartilaginous (1/3) Inner Bone structure (2/3)
Why might it be useful to pull the pinna back and upwards during an otoscopic examination?
As the outer 1/3 of the external acoustic meatusis cartilaginous and sigmoidal in shape. Pulling the pinna helps straighten out the moveable cartilaginous part of the external auditory meatus.
What structures are contained within the skin of the outer 1/3 of the external auditory meatus?
Hair
Sebaceous glands
Ceruminous gland
What is epithelial migration?
The natural cleaning function in the external auditory meatus. Surface of the skin moves laterally from the lateral surface of the tympanic membrane out of the external auditory meatus via the ear canal.
How do we view the external auditory meatus?
Otoscope
What are common conditions affecting the external auditory meatus?
Wax/foreign bodies causing occlusion
Otitis externa
What is Otitis Externa?
Inflammation of the external Acoustic Meatus. Presents with ear discomfort/pain on moving tragus or pinna/itchiness/discharge/possible temporary hearing loss
What are risk factors for otitis externa?
‘Swimmers ear’ - moisture in the EAM providing an ideal breeding ground for bacteria
- Pseudomonas aeruginosa
- Staphylococcus species
What is the treatment of Otitis externa?
Keep EAM dry
Antibiotics
What is a complication of Otitis externa?
Malignant otitis externa / necrotising otitis externa
Bacterial infection becomes invasive and erodes through bone of the ear
Who is most at risk of developing malignant otitis externa?
Immunocompromised
Diabetics
Describe the shape of the tympanic membrane?
Concave
Central depression
What is tympanosclerosis?
Scarring of the tympanic membrane
White plaques seen - evidence of previous injury
What is acute otitis media?
Middle ear pathology resulting from bacterial/viral infection causing build up of inflammatory exudate in the middle ear cavity. Causes the tympanic membrane to become bulge laterally and appear red and swollen. Usually self resolving
How does the tympanic membrane appear in otitis media with effusion?
Tympanic membrane is retracted medially. May see air bubbles due to accumulation of fluid in the middle cavity. Fluid level
What causes a cholesteatoma?
An increase in negative pressure of the middle ear cavity.
Usually secondary to chronic Eustachian tube dysfunction.
Results in pars flaccida of the tympanic membrane being retracted. To form a sac/pocket.
Explain the pathological process of cholesteatoma
Retraction of pars flaccida forms a sac/pocket. Migrating epithelium accumulates in the pars flaccida pocket, trapping stratified squamous epithelium and keratin. This proliferates to form a cholesteatoma.
How can cholesteatoma cause serious consequences?
Cholesteatoma can grow and expand into the middle ear cavity and result in enzymatic bony destruction.
Ossicles damaged/eroded. Mastoid/petrous bone erosion. Interfere with cochlea
What are the signs and symptoms of cholesteatoma?
Otoscopy - pars flaccida on the superior aspect of tympanic membrane retracted. Tympanic membrane also retracted. Crusty lesion around pars flaccida.
Painless, smelly otorrhoea, may have hearing loss depending on extent and damage by cholesteatoma
