Ear
I. Outer Ear
A. Auricle/Pinna – direct sound waves into the ear; ear flap
1. Problems
a. alopecia
b. swelling
c. hematomas
d. parasites
B. External Auditory Canal – secretes waxy material to protect and lubricate
1. Problems
a. foreign body
b. parasites
c. bacteria/yeast infections
II. Middle Ear
A. Tympanic membrane (ear drum) – sound waves strike this membrane and amplifies; should
be white in appearance
B. Eustachian tube – establishes communication between the tympanic cavity and the nasal
pharynx; adjusts the pressure of air in the cavity to the external pressure
C. Ossicle (“small bone”) – amplify sound 40 times
1. malleus (hammer)
2. incus (anvil)
3. stapes (stirrup)
III. Inner ear – transmits sound to the brain and provides equilibrium
A. Bony labyrinth
1. Vestibule – contral portion
2. Semicircular canals – equilibrium
B. Membranous labyrinth – fluids to provide a medium to conduct vibrations
C. Cochlea (snail) – acoustic labyrinth; hairs vibrate and transform into electrical sensory
impulses carried to the brain
IV. Pathological Conditions
A. Noninflammatory Alopecia – hair loss on the pinna without inflammation; hormone
imbalance
B. Pinnal Alopecia – hereditary predisposition in Dachshund, Chihuahuas, Whippet
C. Actinic Dermatoses – most seen in white cats; chronic sun exposure to the ears cause’s hair
loss and skin problems
D. Contact Dermatitis – result of allergies, reaction to medication, or direct irritation
E. Fly strike – fly dermatitis caused by stable flies; flies bite and tear open the skin on the ears
F. Frost bite
G. Aural hematomas – caused by scratching or head shaking; more common in the pendulous
ears
Treated aural hematoma
H. Otitis Externa – most common disease in dogs and cats
1. Causes: abundance of hair in the canal, build-up of wax, foreign body, parasites,
moisture in the canal, allergies
2. Clinical signs: head shaking, scratching at the ears, inflammation, head tilt, discharge,
odor
3. Treatment: clean the ear and make sure it is dry; apply topical therapy
I. Otitis Media – can result from otitis externa or ruptured ear drum (21 days to heal)
1. Clinical signs: facial nerves affected – drooping lips, drooling, drooping face on one
side, head tilt
V. Ceruminolytic Agents – breaks down wax
Cerumene, Cerusol, Murine ear, Panotic