Chapter 8: The Outer Ear Flashcards
Development of the Outer Ear
-28 days after conception, the pharyngeal arches develop the head and neck
-auricle and external auditory canal
Function of Auricle/Pinna
-gather sound waves and funnel them into the external ear canal
-localization aid
-enhance high frequency sounds
External auditory meatus vs external auditory canal
meatus: the ear’s opening
canal: the actual tube leading to the tm
External Auditory Canal Functions
-Protect the TM from trauma and foreign objects
-Keep TM at constant temp 98.6F
-Sound filter
Umbo
-Point of greatest retraction by malleus
-This is seen in middle ear infections when negative pressure is retracting the TM into the middle ear. Observed with a type C tymp.
Disorders of the auricle
-hearing tests ignore the auricle
-microtia (small pinna)
-anotia (absent pinna)
Atresia
-Lack of ear canal
-Seen in Treacher Collins syndrome, Charge syndrome, burns/trauma
Stenosis
-narrowing of the External ear canal
-may not directly cause a hearing loss
-can produce an artificial conductive hearing loss if inserts are not used.
Foreign Bodies in ear
-Total occlusion may cause hearing loss
External Otitis
-Infection of external auditory canal
-Most commonly caused by bacteria but can be fungal too
-Mild hearing loss may be present
Growths in the External ear canal
-Only produce hearing loss if it occludes the EAC
-Osteomas: bony tumors
-Extoses: outward projections of surfaces of bone
Cerumen Removal Methods
-Curettes (scooping)
-Suction
-Irrigation (water)
Perforations of the TM Causes
-excessive pressure build up during middle ear disorder
-direct trauma
-sudden pressure in EAC
-rapid changes in EAC pressure
TM perforation treatment
-Most heal spontaneously
-Surgical repair (myrigoplasty)
Thickening of the TM
-Tympanosclerosis: TM thickens or scars due to infection
-Could cause less mobility of the TM resulting in conductive hearing loss
-Doesn’t respond well to any treatment
