Functions of the ear
Hearing and balance
Three areas of the ear
External, middle, and inner
Auricle, external auditory canal, tympanic membrane
External auditory canal (meatus)
Within the temporal lobe, ceruminous glands
Separates external and middle ear, fibrous CT
Ossicles, openings, muscles
Malleus, incus, stapes
Oval window- Superior, stapes rests on it
Round window- Inferior
Pharynogotympanic (auditor) tube, or Eustachain tube- Connects with nasopharynx
Stapedius, tensor tympani
Bony labyrinth, membranous labyrinth
Made from petrous portion of temporal lobe, filled with perilymph, consists of: cochlea, 3 semicircular canals, vestibule
Filled with endolymph, consists of: cochlear duct (w/in cochlea), 3 semicircular ducts, utricle and saccule
Bony upper scala vestibuli and lower scala tympani: filled with perilymph. Middle membranous scala media or cochlear duct contains Organ of Corti; filled with endolymph. Upper vestibular membrane and lower basilar membrane which supports Organ of Corti
Organ of Corti
Rests upon basilar membrane, has supporting cells, hair cells (inner and outer), tectorial membrane on top of hairs, cochlear branch of vestibulocochlear nerve cranial nerve VIII
Physiology of Hearing
Passage of sound waves
Pressure waves in cochlea
Movement of hairs in Organ of Corti
Depolarization and passage of impulse
High frequency sound-stimulate hair cells near oval window; low frequency near apex
Vestibular branch of VIII cranial nerve
Role of macula in utricle and saccule within vestibule
Role of semicircular ducts with semicircular canals
Ampulla at base containing crista ampularis
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