Audiology Chapter 8 – The Outer Ear

Vocabulary flashcards covering anatomy, development, and common disorders of the outer ear as presented in Chapter 8 of Introduction to Audiology (13th ed.).

Outer Ear

Portion of the auditory system consisting of the auricle (pinna), external auditory canal, and tympanic membrane; gathers and funnels sound toward the middle ear.

Auricle (Pinna)

Visible, cartilaginous part of the ear; funnels sound, enhances high frequencies, and helps with sound localization.

External Auditory Canal (EAC) / External Auditory Meatus (EAM)

Skin-lined passage extending ~2.5 cm from the concha to the tympanic membrane; outer third is cartilaginous with hairs and ceruminous glands, inner two-thirds are bony.

Tympanic Membrane (TM)

Thin, semi-transparent, three-layered disk marking the border of outer and middle ear; vibrates in response to sound.

Pharyngeal Arches

Series of embryonic tissue bands that form head and neck structures; first two arches give rise to the auricle and external canal.

Ectoderm

Outer embryonic layer of pharyngeal arches; contributes to skin layer of the external canal and tympanic membrane.

Mesoderm

Middle embryonic layer forming connective tissue and muscle; provides fibrous layer of the tympanic membrane.

Endoderm (Entoderm)

Inner embryonic layer lining the pharyngeal arches; becomes mucous membrane of the middle ear and inner TM layer.

Tragus

Small projection in front of the ear canal opening; develops from first pharyngeal arch.

Helix

Rim of the auricle; originates from the second pharyngeal arch.

Antitragus

Small bump opposite the tragus on the lower auricle; formed from the second arch.

Concha (Cavum & Cymba)

Bowl-shaped depression leading into the ear canal; entrance for sound into the EAC.

Osseocartilaginous Junction

Meeting point of the cartilaginous outer third and bony inner two-thirds of the external auditory canal.

Umbo

Point of greatest inward retraction on the tympanic membrane where the malleus attaches.

Pars Tensa

Taut, thick portion covering most of the tympanic membrane; primary vibrating area.

Pars Flaccida

Superior, slack portion of the tympanic membrane lacking fibrous layer; more prone to pathological changes.

Cone of Light

Triangle-shaped light reflex seen on the tympanic membrane during otoscopy due to its concavity.

Conductive Hearing Loss

Hearing impairment caused by blockage or dysfunction in the outer or middle ear; air-bone gap never exceeds ~60 dB.

Microtia

Congenital condition in which the pinna is abnormally small; can be unilateral or bilateral.

Anotia

Complete congenital absence of the pinna, usually accompanied by a narrowed or absent ear canal.

Basal Cell Carcinoma (Ear)

Most common skin cancer; frequently arises on the helix due to UV exposure and is curable with early treatment.

Atresia (Ear Canal)

Congenital absence or closure of the external auditory canal; degree of closure determines conductive hearing loss.

Treacher Collins Syndrome

Craniofacial disorder often associated with ear canal atresia, microtia, and conductive hearing loss.

CHARGE Syndrome

Genetic condition that may include external ear canal atresia among its multiple anomalies.

External Otitis (Swimmer’s Ear)

Bacterial infection of the skin of the external auditory canal causing pain, swelling, discharge, and possible conductive loss.

Otomycosis

Fungal infection of the external auditory canal; subtype of external otitis.

Stenosis (EAC)

Abnormal narrowing of the external auditory canal; may predispose to wax blockage but doesn’t itself cause hearing loss.

Collapsing Auditory Canal

Temporary occlusion of the ear canal when supra-aural headphones press the auricle inward, creating artificial conductive loss;

Osteoma

Solitary, benign bony tumor in the bony portion of the external auditory canal; rarely causes obstruction.

Exostosis

Multiple benign bony growths in the medial EAC, often in people exposed to cold water; typically do not occlude the canal.

Cerumen Impaction

Accumulation of earwax that occludes the canal and attenuates sound, producing mild-to-moderate conductive loss.

Cerumenolytic

Chemical agent used to soften earwax before professional removal by curette, suction, or irrigation.

Tympanic Membrane Perforation

Hole or tear in the eardrum due to infection, trauma, or pressure changes; degree and site dictate hearing loss.

Myringoplasty

Surgical procedure to repair a tympanic membrane perforation that fails to heal spontaneously.

Tympanosclerosis

Thickening and scarring of the tympanic membrane with calcium plaques; may add mass and impede vibration.

Air–Bone Gap

Difference between air-conduction and bone-conduction thresholds on an audiogram indicating conductive involvement (≤ 60 dB).