Ear anatomy Flashcards
What is the function of the auricle?
Collect, focus, and direct sound down the funnel-shaped external acoustic meatus to the tympanic membrane
What antibodies have been identified in cerumen?
IgA, IgG and IgM
What is the predominant immunoglobulin in normal and inflamed ears?
IgG for both
What is the function of the Eustachian (auditory) tube?
Equalize pressure on both sides of the tympanic membrane
Name the 2 structures that attach to the malleus
Tympanic membrane and incus
Name the 3 components of the middle ear
Tympanic cavity, 3 auditory ossicles and tympanic membrane
What 2 structures attach to the stapes?
Vestibular window (in contact with perilymph fluid) and incus
Where does the tensor tympani muscle insert?
Malleus
What nerve innervates the tensor tympani muscle?
Branch of trigeminal nerve
Where does stapedius muscle insert?
Stapes
What nerve innervates the stapedius muscle?
Stapedial branch of facial nerve
Where do both the tensor tympani and stapedius muscles originate?
Tympanic bulla
Name the bony structure that houses the cochea
Promontory (where cochlear and vestibular windows are located)
Describe the 3 layers of the tympanic membrane and their origin
Inner epithelium: originates from pharyngeal pouch
Central layer: fibrous connective tissue of pharyngeal wall
Outer layer: stratified squamous epithelium derived from ectoderm of first pharyngeal groove
What is the stria mallearis?
Outline of the manibrium of malleus
Where should a myringotomy be performed?
Caudal ventral quadrant of TM (pars tensa)
Which direction does the manubrium of the malleus face?
C-shaped and concave aspect of the C points rostrally
Where and in what direction does tympanic membrane regenerate?
Radially from the umbo pars tensa
Name the clinical signs of Horner’s syndrome
Ptosis, pupillary miosis, prominent third eyelid, enopthalmia
Where does the annular cartilage insert?
Within the bone of external acoustic meatus
What are the 3 parts of the tympanic cavity?
Dorsal: smallest
Middle (aka tympanic cavity proper): adjacent to TM
Ventral: largest; tympanic bulla with septum bulla
Know how to label this
What are the 2 divisions of the septum bulla in cats?
Pars tympanica: small and dorsolateral
Pars endotympanica: large and ventromedial
Name another dog breed reported to have PSOM other than CKCS?
Boxer, dachshund, and shih tzu
Name the anatomical region where one inserts the ototscopic cone?
Antitragus
What dog breed typically have excessive compound hair follicles in the horizontal ear canal?
Cocker spaniel dogs
What dog breeds have simple hair follicles in the horizontal ear canals?
Greyhounds and mixed breed dogs
What are simple coiled tubular glands that resemble apocrine sweat glands?
Ceruminous glands
Ceruminous glands are composed of an inner secretory layer surrounded by ______ cells on a basement membrane
Myoepithelial cells
What is the normal pH of ear canal epithelium in dogs?
A. 4.6-7.2
B. 6.0-7.4
C. 5.2-7.2
D. None of the above
A. 4.6-7.2 – Normal
B. 6.0-7.4 – Chronic otitis
C. 5.2-7.2 – Acute otitis
What is the gas in the middle ear composed of?
Nitrogen 83%, oxygen 12%, carbon dioxide 4.7%
What is an acoustic reflex?
When the ear is stimulated with a VERY loud sound, the stapedius muscle will contract to protect the middle ear from damaging level of noise
Acoustic reflex is usually absent in patients with what disease?
Middle ear disease
Blood supply to the ear comes from what 2 main arteries?
External carotid artery and vertebral arteries
What is the largest artery to the ear?
Intermediate auricular branch
Name the 4 nerves of the sensory innervation of the pinna
Trigeminal, facial, vagus, second cervical
Which cartilage does NOT contribute to the formation of the externa ear?
A. Auricular cartilage
B. Annular cartilage
C. Scutiform cartilage
D. None of the above
C. Scutiform cartilage
Know how to label this
Can you label the inner and external ear structures of the dog?
You better!
What nerve innervates the rostroauricular and caudoauricular muscles of the pinna?
Motor branches of the facial nerve
What does the external ear consist of?
The auricle (pinna) and external acoustic meatus
What does the middle ear consist of?
The ossicles, tympanic cavity, and bulla
What does the inner ear consist of?
Cochlea and semicircular canals
In horses, how is the junction between the cartilaginous and osseous portions of the external acoustic meatus grossly identified?
An abrupt change from pigmented to nonpigmented epithelium.
Match the Tympanic membranes: Pig, Goat, Horse, Dog (ignore the bottom 2 images)
A, Horse. In the horse, the tympanic membrane (tympanum) is more round than other species. The manubrium of the malleus forms a very shallow arc and is centrally located in the tympanum.
B, Dog. The tympanum is oval to comma-shaped, and the manubrium of the malleus is C-shaped.
C, Pig. Similar to the dog, but the manubrium of the malleus is shorter and straighter.
D, Goat. Ruminants tend to have a more triangular-shaped tympanic membrane. In both pigs and ruminants, the manubrium of the malleus is more rostral and medial than in other species.
