outer, middle ear

Tragus

hairy point/ goat

Lobule

connected to antitragus

Inferior aspect of the deeper inner part of the ear

tragus + antitragus

Headphones position

Between antitragus and tragus

Helix

twisted

Nerves through the internal acoustic meatus

Vestibulocochlear (CN VIII) and facial (CN VII)

Nerves through the jugular foramen

internal jugular vein, Glossopharyngeal nerve (CN IX), Vagus nerve (CN X), Spinal Accessory (CN XI)

Mandibular fossa

depression for articulation with mandible

Zygomatic process

projection forming of zygomatic arch

Petrous

stony, rocky, hardest, dense bone; protects cochlea/ semicircular canals

Tympanic

tympanum = drum; forms walls around ear canal, linked with ear drum

Tympanic membrane

separates the external ear from the middle ear

Parts of the middle ear

lateral wall (eardrum), Internal wall (oval window + round window), Posterior wall (back- mastoid antrum), Anterior wall (front- opening of eustachian tube)

Mastoid antrum

Cavity linking middle ear with mastoid cavity

Eustachian tube location

connects middle ear to nasopharynx

Structures located at the middle ear

oval window (Superior), Round window (inferior)

Functions of the Eustachian tube

1. Equalises pressure across tympanic membrane; 2. Protects from reflux of fluids from nasopharynx; 3. Clears out middle ear secretions

Main structures in the middle ear chamber

ossicles (malleus, incus, stapes)

Ossicles

small bones

Incus

anvil

Malleus

hammer

Stapes

stirrup

Concha

shell (resembles a shell shaped cavity)

Auricle

little ear

Pinna

wing / feather

Structures of the external ear

helix, Anti helix, Concha, Tragus, Antitragus, Lobule, Opening of external auditory meatus

Great auricular nerve

C2,3

Lesser occipital nerve

C2

Structural components of the external auditory meatus

Dermis and cartilage

Importance of the external auditory meatus for otoscopy

Because the external auditory meatus (ear canal) has flexures (S-shaped bends) that block the view of the tympanic membrane, the pinna must be pulled to straighten the canal for proper examination.

Technique for otoscopy in adults

Pull back and up

Technique for otoscopy in children

Pull back and down

Two main regions on the tympanic membrane

Pars flaccida - floppy, loose, small; pars tensa - tense, stretched, main drum for sound transmission

Landmarks on the tympanic membrane

Lateral malleolar process, manubrium of malleus, umbo, cone of light, fibrocartilaginous ring

Structures shown in tympanic membrane histology

External acoustic meatus, tympanic membrane, middle ear (tympanic cavity), compact bone, cartilage

What fills the middle ear

Air

Purpose of the middle ear

Transmits sound from air to inner ear fluid, vibrates tympanic membrane, ossicles amplify and transmit vibration to oval window, vibration becomes fluid waves in inner ear (perilymph)

Nerve running across the middle ear cavity

Chorda tympani (Branch of CN VII facial nerve)

Function of the Chorda tympani

Carries taste from anterior 2/3 of tongue; parasympathetic to submandibular / sublingual glands

Location of the tympanic plexus

Walls of the middle ear cavity

Innervation by the tympanic plexus

Mucous membrane lining the lateral walls of the middle ear, Pharyngotympanic (eustachian) tube, Mastoid air cells

Sympathetic fibres contributing to the tympanic plexus

Caroticotympanic nerves from the internal carotid plexus

Nerve arising from the tympanic plexus to the parotid gland

Lesser petrosal nerve (preganglionic parasympathetic → otic ganglion → parotid gland)

Inner ear structures

Cochlea, vestibule, semicircular canals

Role of the tensor tympani

Pulls manubrium of malleus medially, tenses tympanic membrane, dampens movement to loud noise (tympanic reflex)

Nerve innervating tensor tympani

Mandibular division of trigeminal nerve CNV3

Role of the stapedius

Dampens movement of stapes at the oval window

Nerve innervating stapedius

Branch of facial nerve CNVII

Structures opening into the nasopharynx from the ear

The pharyngotympanic (Eustachian) tube

Muscles acting on the pharyngotympanic tube

Tensor veli palatini and levator veli palatini

Otitis externa

Infection/inflammation of external auditory canal; Symptoms include pain, itching, discharge

Otitis media

Infection/inflammation of the middle ear cavity; Symptoms include ear pain, fever, hearing loss, often after URTI

Cerumen impaction

Build up of ear wax in external auditory meatus; Symptoms include conductive hearing loss, discomfort, blockage sensation

Perforated tympanic membrane

Tear/hole in the tympanic membrane; Causes include infection (otitis media), trauma; Symptoms include sudden ear pain, hearing loss, discharge; Investigation includes otoscopy (visual hole/tear in eardrum)

Eustachian tube changes with age

Children: shorter + more horizontal → higher risk of otitis media; Adults: longer + angled → less prone to infection

Ways the middle ear amplifies sounds

1. Tympanic membrane area ~ 17x larger than oval window → pressure amplification; 2. Lever action of malleus + incus = extra amplification; 3. Round window moves opposite oval window → allows fluid movement in cochlea

Difference between round vs oval window functions

Oval: input of sound waves; Round: pressure release

Importance of stapedius and tensor tympanic reflex

Protective mechanisms for loud sounds

Auricular muscles

Superior auricular, anterior auricular, posterior auricular

Nerve innervating auricular muscles

Facial nerve CNVII

Branches of facial nerve supplying auricular muscles

Posterior auricular nerve - posterior auricular muscle; Temporal branch (further branches) - anterior and superior auricular muscles

Function of auricular muscles in humans

Small, rudimentary movement of ear (not very functional in humans, stronger in animals like cats)

Mnemonic for auricular muscle innervation

Not provided in the note

Acute otitis media

An infection in the middle of the ear indicated by bulging opaque tympanic membrane and inflammation.

Route of spread for otitis media

From nasopharynx → eustachian tube → middle ear.

Why is otitis media more common in infants?

Infants have shorter, more horizontal Eustachian tube, making them more prone to obstruction and reflux.

Treatment for persistent otitis media with effusion

Myringotomy with grommet insertion - a small incision in the tympanic membrane with a tube to ventilate the middle ear.

Structure dysfunction in glue ear

Eustachian tube - poor drainage and ventilation cause fluid to collect in the middle ear.

Structures in the middle ear damaged by prolonged fluid

Ossicles (malleus, incus, stapes) leading to hearing loss.

Infected part of temporal bone in mastoiditis

Mastoid air cells in the mastoid process.

Usual route of infection to mastoid air cells

From the nasopharynx → pharyngotympanic tube → middle ear → mastoid antrum → mastoid air cells.

Structure incised in myringotomy for mastoiditis

Tympanic membrane.

Dangerous complication if mastoiditis is untreated

Tegmen tympani (thin bone separating middle ear and cranial fossa).

Conditions from untreated mastoiditis

Meningitis or a brain abscess (and potentially osteomyelitis of temporal bone).

Differentiating Bell's palsy from a stroke

Bell's palsy - patient cannot wrinkle their forehead (LMN lesions); Stroke - forehead movement is preserved (UMN dual innervation).

Exit point of facial nerve from temporal bone

Stylomastoid foramen.

Three key branches of facial nerve before exiting stylomastoid foramen

Greater petrosal nerve → lacrimal gland (parasympathetic); Nerve to stapedius → stapedius muscle; Chorda tympani → taste anterior 2/3 tongue + salivary gland innervation.

Symptoms affected nerves in patient

Dry eyes → greater petrosal nerve; Hyperacusis (sound sensitivity) → stapedius nerve; Loss of taste (anterior 2/3 of tongue) → chorda tympani.

Virus causing Bell's palsy

HSV-1 (herpes simplex virus).

Ramsay Hunt syndrome

Reactivation of Varicella zoster virus in the geniculate ganglion leading to facial nerve palsy plus vesicular rash on pinna/external auditory meatus.

Triggers for Ramsay Hunt syndrome

Stress or immunosuppression.

Common bacterial causes of otitis externa

Pseudomonas aeruginosa; Staphylococcus aureus.

Initial treatment for otitis externa

Keep ears dry (ear plugs/swimming cap); antibiotic ear drops.

Complication from untreated otitis externa

Tympanic membrane perforation causing severe pain and hearing loss.

Exostosis

Bony outgrowth/spur, in this case, external auditory exostosis ('surfer's ear').

Management of surfer's ear

Surgical referral to remove exostoses.

Diagnosis of otitis externa clinically

With otoscopy — red, swollen external canal with possible discharge.

Finding on otoscopy indicating otitis media

Bulging, inflamed tympanic membrane, sometimes with effusion.

Condition shown on otoscopy by a wax plug

Cerumen impaction.

Clinical investigation of hearing loss

Audiometry; tuning fork tests (Rinne and Weber); otoscopy.