The Senses: The Ear

The External Ear

Collects sound waves, channels them into ear canal

Rich in cartilage Continues to grow

throughout life!

Disorder: Cauliflower Ear

Trauma/Bruising leads to… accumulation of blood, tissue

Builds up between skin, cartilage

Disorder: Tophi

Small nodules filled with crystals of uric acid

Common in patients with gout

Darwin’s Tubercle

Nodule at the helix Congenital (inherited)

Tympanic membrane/Eardrum

Divides external and middle ear Vibrations of air cause this

membrane to vibrate, like a drum Diagnostic information

Redness, inflammation,Bulging = infection

Vestibulocochlear nerve (VIII)

Eustachian tube

External Auditory Meatus/Canal

Leads from auricle/pinna to tympanic membrane/eardrum

Collects sound waves Outer 1/3 contains:

Many short hairs Ceruminous glands – produce wax

(cerumen)▪ Collects debris▪ May accumulate, absorb/block sound waves

Middle Ear

Middle Ear

Hollowed area of temporal bone (labrynth) Houses three very small bones (ossicles)

Malleus (hammer) Incus (anvil) Stapes (stirrup)

Transmits sound from tympanic membrane to oval window

Eustachian (auditory) tube – connects throat with middle ear – equalizes pressure

Condition: Otitis media

Blocked/inflamed Eustachian tube due to infection Can’t equalize pressure discomfort

Inner Ear

Inner Ear Anatomy

Complex spaces in the temporal bone, called bony labyrinth Filled with watery perilymph Divided into:▪ Vestibule▪ Semicircular canals▪ Cochlea

Cochlea

“Tube-in-a-tube” Membranous labyrinth

Filled with thicker endolymph

Semicircular Canals 3 half-circle canals Oriented at right angles to each

other Contain ampulla

Contains crista ampullaris▪ Hairlike extensions suspended in endolymph

Generates nerve impulse when head moves