Unit 2: Ear Structure & Function Flashcards
What is the landmark for cytology and otoscope insertion?
intertragic incisure
What are the cartilage types of the external ear?
Auricular (vertical canal) and annular (horizontal canal)
How do the external canal cartilages interact with each other?
Auricular cartilage overlaps annular cartilage - allows for flexibility and movement
Where does debris like to build up in the external canal?
In the little “dip” at the end of the vertical canal
How can you keep dogs from jumping when using an otoscope?
(they jump from the scope hitting the fold)
Take the pinna and pull it out and away to get the scope under the fold easier
What are the lengths of the auricular and annular cartilages?
Auricular = 4.1 cm
Annular = 1.2 cm
What is the diameter of the external canal at thr tragus?
5.8 cm
What is the mean pH of the ear canal in dogs?
6.1 in males, 6.2 in females
What is the relative humidity of the external canal?
80%
What is the temperature of the external canal?
0.6ºC lower than rectal
What are the types of pinnae and which one has more otitis?
Erect vs. pendulous
The volume of the ear canal impacts _____.
treatment
The length of the ear canal impacts _____.
examinations
What does the skin of the ear canal contain?
Sebaceous and apocrine (ceruminous) glands, hair follicles
What types of inflammation/infection involve the structures of the skin of the canal?
Folliculitis, adenitis, ruptured sweat glands
What is the technical term for ear wax?
cerumen
What are the components of cerumen?
Secretions of sebaceous glands, ceruminous (apocrine) gland secretions, epithelial cells (keratinocytes)
What is the lipid content of cerumen made of?
Margaric, oleic, stearic, and linoleic fatty acids
What are the functions of cerumen?
Lubrication, hydration, protection
Lipid content of cerumen decreases ___ to ___% in chronic otitis externa.
49%, 24%
What can dilute lipid content of cerumen?
Hyperplasia of the apocrine glands
What is the “self-cleansing” mechanism of the ear?
epithelial migration
What can a prominent pars flaccida resemble in the ear canal?
Tumors - can use pneumo-otoscopy to test
What is the point of pneumo-otoscopy?
Gentle blowing or use of a bulb to create positive pressure in the ear canal, making the pars flaccida move
What are the smallest muscles in the body?
tensor tympani and stapedius
What is the nerve bundle that runs thru the middle ear?
chordae tympani
What is the smallest bone in the body?
stapes
What cells line the middle ear side of the tympanic membrane?
VERY thin layer of cuboidal epithelium
What cells line the ear canal side of the tympanic membrane?
Thin layer of stratified squamous epithelium
What things live in between the 2 cell layers of the tympanic membrane?
Lymphatics, vessels, collagen
What are some things in the cat ear that are different from the dog?
They have a bony septum that divides the middle ear into 2 compartments, their external canal doesn’t have a deep “trap” like the dog’s, and it is a smaller diameter (difficult to pass some scopes)
How is the tympanic membrane of the cat different than the dog?
It is more transparent, the septum obstructs view, less hair visible
T/F: The malleus of cats is straighter than the dog’s.
True
The middle ear is housed in the _____ bone.
temporal
How many chambers does the middle ear have?
2
What cavities are behind the ear drum?
Epitympanic, tympanic, ventral (fundic)
What cells line the middle ear?
Modified respiratory epithelium (some ciliated and secretory cells)
What other structures are in the middle ear?
Nerves, vessels, ossicles, muscles
What are the 4 main components of the middle ear?
- Ventral/fundic cavity (tympanic bulla)
- Tympanic cavity proper
- Epitympanic recess/cavity
- Promontory
What do striations on the tympanic membrane indicate?
That it is a super young dog
What middle ear structures can be seen on otoscopic exam?
Ventral cavity, promontory, edge of bulla
What does the stapes attach to?
vestibular window
What general nerve types are found in the middle ear?
Parasympathetic and sympathetic
A
malleus
B
stapes
C
vestibular window
D
nerves
What cranial nerve exits into the middle ear?
facial nerve
What foramen does the facial nerve exit out of?
stylomastoid foramen
What is the auditory tube?
Communication between the pharynx and the middle ear
Where does the auditory tube enter?
Enters bulla at rostral end of middle ear
What is the significance of the auditory tube?
It is a mjor pathway for entrance of infectioous agents
Where is the cochlea contained?
Within the petrous temporal bone
What are general pathologic changes that can happen in the ear?
Inflammation, glandular hyperplasia, epidermal hyperplasia, fibroplasia, ossification
What can environmental changes lead to in otitis externa?
Increased temperature of ear canal, increased apocrine secretions (increased humidity, dilution of lipid content of wax), proliferation of micro-organisms
Chronic, uncontrolled inflammation results in _____ changes.
progressive
_____ hampers treatment!
fibrosis
What is a key point to make with clients regarding diagnosis and management?
There is a need for aggressive diagnosis and management EARLY in the process
What is the minimum treatment for folliculitis and furunculosis?
21-30 days
What is adenitis?
Inflammation of the apocrine (ceruminous) glands
Adenitis is present in all _____ otitis cases.
chronic
What are the defense mechanisms of the ear?
Conformation, hair, cerumen, self-cleansing mechanism
What are the 7 best practices in the management of otitis?
- Use appropriate diagnostics
- Prepare the canal for treatment
- Choose treatment wisely
- Medications must be administered properly
- Use quality control to evaluate treatment
- Consider long-term maintenance therapy
- ID and control primary factors
