anatomy of ear

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  1. development of the ear
    • develops from pharyngeal arches and have 3 layers of tissue, ectoderm, mesoderm, and endoderm
    • develops after 2nd fetal month
    • tm begins to form by the beginning of the second embryonic month
  2. EAC
    • External auditory canal
    • 1 inch in adults
    • elliptical 
    • lined with skin
    • different angle for children than adults
  3. purpose of the eac is to
    • protect tm
    • constant temp in the canal
    • constant humidity 
    • efficient transfer energy to tm
  4. tympanic membrane
    • border between outer and middle ear
    • 3 layers
    • acts as a loud speaker
    • tympanic annulus holds membrane in place
    • pars tensa is taut surface area at the bottom
    • pars flaccida is at top and does not repair easily
    • pressure waves cause tm to vibrate producing sounds
  5. CONDUCTIVE LOSS possible causes of hearing loss in the outer ear include
    • hearing loss never exceeds 60 db
    • disorders of auricle
    • atresia of eac
    • stenosis of canal
    • collapsing of canal
    • foreign body
    • growths
    • earwax perforation of tm
    • tympanosclerosis
  6. middle ear
    • roof separates middle ear cavity from brain
    • in front is carotid artery
    • behind is mastoid process
  7. middle ear
    eustachian tube
    • connects middle ear to back of the throat and nose
    • 30 angle in adults
    • lined with ciliated epithelium
    • kept closed by the spring mechanism of cartilage and opened by the action of 3 sets of muscles at the orifice of the tube in the nasopharynx
    • opens during yawning, swallowing, excessive air pressure is applied from the nose
    • this is the ventalator
  8. middle ear
    • malleus (hammer)
    • incus (anvil)
    • stapes (stirrup)
  9. middle ear
    • embedded in the fibrous portion of the tm
    • tip ends in the appro, center of the tm
    • pulls the center of the tm inward resulting int he concave shape
    • UMBO is point of greatest retraction
  10. middle ear
    ossicular function
    • carry the sound waves from air filled external aud canal to the fluid filled inner ear
    • vibrations of the tm are carried to the oval window
    • acts as a single unit, or you won't be hearing
    • acoustic energy to mechanical energy
  11. middle ear
    • stapedius muscle
    •      attaches to stapes
    •      acoutic reflex
    • tensor tympani muscle
    •      attaches to malleus
    •      not thought to be responsive to sound
    •      air blast, touch, temp change
    • muscles contract in response to sound, acoutic reflex
  12. hearing loss of the middle ear
    • otitis media-middle ear infect
    • tympanic membran perforation
    • ossicular chain discontinuity-bone freezes or broken
    • otosclerosis-foot plate freezes
    • congenital disorders-malformation of the bones in the ear
  13. inner ear
    • function is to transduce the mechanical energy into bioelectrical energy
    • made up of semicircular canals (balance) and vestibule and cochlea (microphone)
  14. inner ear
    • 2.5 turns
    • perilymphatic space=surrounds the membranes of labyrinth
    • endolymphatic space=within memebranous labyrinth
  15. inner ear
    organ of corti
    epithelium of the inner ear is called organ of corti, it is larger and the basilar membrane on which it sits is longers as it gets further away from the base of the cochlea
  16. inner ear
    3 cavities
    • scala vestibuli
    • scala media
    • scala tympani
    • fluid filled with endolymph (SM) and perilymph (SV and ST)
  17. causes of sensorineural hearing loss, inner ear loss
    • rh factor-blood compatibilty
    • heredity
    • trauma
    • high fevers
    • drugs
    • presbycusis-high freq hearing loss
    • menieres disease-vertigo
    • noise
    • rubella
    • cytomegalovirus
    • high fever 
    • drugs-myosin
  18. inner ear
    vestibular system
    • balance 
    • semi circular canals
    • fluid filled
    • shares boy structure with cochlea
    • shares same bony memebranous structure with cochlea
  19. afferent and efferent
    • aff-to brain
    • eff-from brain
  20. conductive hearing loss
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anatomy of ear
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