DISEASES OF THE EXTERNAL EAR (AB) Flashcards
What structures make up the outer ear?
Auricle and external auditory canal (EAC), up to the tympanic membrane.
What type of epithelium lines the external auditory canal?
Keratinized stratified squamous epithelium.
How long is the external auditory canal (EAC)?
Approximately 2.5 cm.
What marks the demarcation between the external and inner ear?
The tympanic membrane.
What is the composition of the auricle?
Mostly skin-lined cartilage.
What is the composition of the external auditory meatus?
40% cartilaginous (lateral 1/3), 60% bony (medial 2/3).
How does the skin differ in the cartilaginous and bony portions of the EAC?
Cartilaginous portion has thicker skin with a soft dermal layer; bony portion has thicker skin (1/2 to 1 mm).
What shape is the external auditory canal (EAC)?
S-shaped.
How should the ear be pulled to straighten the EAC in adults?
Backward, upward, and outward.
How should the ear be pulled to straighten the EAC in infants?
Backward and downward.
Where is the narrowest portion of the external auditory canal?
At the bony-cartilage junction, called the isthmus of the EAC.
What cranial nerves provide innervation to the external ear?
Cranial nerves V, VII, IX, and X.
What arteries supply the external ear?
Superficial temporal, posterior auricular, and deep auricular branches.
How does venous drainage of the external ear occur?
Through the superficial temporal and posterior auricular veins.
What is the most common cause of impacted cerumen?
Use of Q-tips.
What is the criterion for diagnosing impacted cerumen?
Cerumen must occlude the entire lumen of the EAC.
Where are the sebaceous and apocrine glands that produce cerumen located?
In the cartilaginous third of the external ear, where ear hairs are found.
What are two types of cerumen?
Wet and dry.
What methods are used to remove impacted cerumen?
Curette under direct visualization, thin suction tip, or water irrigation if the tympanic membrane is intact.
Why should irrigation be avoided in some cases of impacted cerumen?
If a foreign body is present, irrigation could push it deeper, causing complications.
When should cerumen not be irrigated?
When the tympanic membrane is perforated.
What substances can be used to soften cerumen?
Cerumenolytics (docusate sodium, paradichlorobenzene), oil, hydrogen peroxide.
What are the primary causes of trauma to the external ear?
Lacerations, hematomas, burns, frostbite, cellulitis, and perichondritis.
What is the difference between lacerations and incised wounds?
Lacerations have clean edges from blunt trauma, incised wounds are from sharp objects.