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The Outer Ear SPA 4302 Summer 2007 Development of the Outer Ear • About __________ after conception the pharyngeal arches develop (bulges on the area of the embryo that will later develop into the head and neck) • As many as ____ all separated by grooves and clefts • First three: – __________ arch – __________ arch – ____________________ arch Development of the Outer Ear • Each of the arches has three layers – _______________ (outer layer) – _______________ (middle layer) – _______________ (inner layer) • Each arch contains four components: – An artery, muscle and cartilage (from mesoderm) – Nerve (from _______________) • Aurical develops from the first 2 pharyngeal arches • EAC develops from the first pharyngeal groove • TM develops from ______________: inner layer from endoderm, middle layer from mesoderm, and outer layer from ectoderm External Auditory Canal • lateral portion-__________ • medial portion-_________ • lined with epidermal (skin) tissue • hairs grow in lateral part • cerumen (ear wax) secreted in lateral part. • Usually curved. Outer Ear Functions 1 • Amplification / Filtering -- 1500 to 7000 Hz increased by ________________ -- produced by resonance of Concha (_______ kHz) & E.A.Canal (_____________ Hz) Outer Ear Functions 2 • Protection -- medial displacement of ___________ -- curvature of canal -- _____________ -- cerumen -- _____________ Outer Ear Functions 3 Localization -- The ability to _________________ ____ of a sound source Otoscopy • Viewing outer ear and TM Looking for: • _____________, • Evidence of infection • Other __________ Lateral Process (Malleus) = Annulus Malleus Manubrium Umbo Cone of Light Epidermal migration produces “wrinkles” Disorders of the Pinna: • Microtia- ___________________________ • Anotia- ____________________________ • Congenital malformation associated with syndromes and disorders • _____________- surgery performed to correct a pinna that either protrudes markedly from head or is pinned to closely Disorders: • Blockage: with earwax, foreign bodies, pus. • Otitis Externa: ________________. – Fungal or Bacterial in origin. – More frequent in ears with small canal • openings that cannot dry out as easily. – This is also sometimes a problem for people wearing _____________-. Otitis Externa Cerumen A Cerumen Tunnel Car Accident Victim Who just didn’t “feel right” afterward… Another Foreign Object Exostoses: Benign bony growths in the outer ear canal • Contrast with Osteomas A False Tympanic Membrane • A layer of dead skin cells builds up in persons who use earplugs or some hearing aids frequently Injuries to Ear Canal A Q-tip Victim Squamous Cell Cancer Malformations: congenital, traumatic or surgical. • ______________: external ear is small, malformed • ______________: ear canal is closed off. • Post-cancer surgery. Congenital Malformation Microtia Anotia: Pre- and Post-Op Mastoiditis Hearing Loss accompanying these disorders: • Blockage or atresia: – moderate ________________ hearing losses. – usually medically or surgically treatable. – additional HL if _______________--associated problems w/ cochlea • Surgical or traumatic: – ___________- frequency conductive. – prosthetics available, expensive.