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the human ear

  1. Anatomy of the EarAnatomy of the Ear Stefan SivkovStefan Sivkov Dept. of Anatomy, Histology andDept. of Anatomy, Histology and EmbryologyEmbryology
  2. Major Divisions of the EarMajor Divisions of the Ear Peripheral Mechanism Central Mechanism OuterOuter EarEar MiddleMiddle EarEar InnerInner EarEar VIIIVIII CranialCranial NerveNerve BrainBrain
  3. External ear, Auris externa Auricula Meatus acusticus externus Middle ear, Auris media Cavitas tympani Membrana tympanica Ossicula auditus Tuba auditiva Inner ear, Auris interna Labyrinthus membranaceus - Labyrinthus vestibularis - Labyrinthus cochlearis Labyrinthus osseus - Vestibulum - Canales semicirculares ossei - Cochlea - Meatus acusticus internus
  4. Outer EarOuter Ear Pinna External Auditory Meatus Pinna Preauricular Tags Preauricular Pits EAM Cerumen Function EAM resonance
  5. Function of Outer EarFunction of Outer Ear  Collects soundCollects sound  LocalizationLocalization  ResonatorResonator  ProtectionProtection  SensitiveSensitive (earlobe)(earlobe)
  6. PinnaPinna  The visible portion that isThe visible portion that is commonly referred to ascommonly referred to as "the ear""the ear"  Helps localize soundHelps localize sound sourcessources  Directs sound into the earDirects sound into the ear  Each individual's pinnaEach individual's pinna creates a distinctive imprintcreates a distinctive imprint on the acoustic waveon the acoustic wave traveling into the auditorytraveling into the auditory canalcanal
  7. External Auditory MeatusExternal Auditory Meatus  Extends from the pinna to the tympanicExtends from the pinna to the tympanic membranemembrane – About 26 mm in length and 7 mm in diameter inAbout 26 mm in length and 7 mm in diameter in adult ear. – Size and shape vary among individuals.Size and shape vary among individuals.  Protects the eardrumProtects the eardrum  ResonatorResonator – Provides about 10 decibels (dB) of gain to theProvides about 10 decibels (dB) of gain to the eardrum at around 3,300 Hertz (Hz).eardrum at around 3,300 Hertz (Hz).  The net effect of the head, pinna, and earThe net effect of the head, pinna, and ear canal is that sounds in the 2,000 to 4,000 Hzcanal is that sounds in the 2,000 to 4,000 Hz region are amplified by 10 to 15 dB.region are amplified by 10 to 15 dB. – Sensitivity to sounds greatest in this frequencySensitivity to sounds greatest in this frequency regionregion – Noises in this range are the most hazardous toNoises in this range are the most hazardous to hearinghearing
  8. Outer earOuter ear Tissues:Tissues: elastic cartilage covered with skinelastic cartilage covered with skin A.A. Meatus acusticus externusMeatus acusticus externus besides the hairbesides the hair follicles and fat glands contains:follicles and fat glands contains: GlandulaeGlandulae ceruminosaeceruminosae –– modified sweatmodified sweat glands on the lateral wall of the canalglands on the lateral wall of the canal.. ССerumerumееnn (ear wax) combination of wax and(ear wax) combination of wax and fat glands secret and desquamated epithelialfat glands secret and desquamated epithelial cellscells..
  9. Middle EarMiddle Ear Tympanic Cavity Tympanic Membrane Ossicles Middle Ear Muscles Eustachian Tube Mastoid
  10. Function of Middle EarFunction of Middle Ear  ConductionConduction – Conduct sound from the outer ear to the inner earConduct sound from the outer ear to the inner ear  ProtectionProtection – Creates a barrier that protects the middle and inner areasCreates a barrier that protects the middle and inner areas from foreign objectsfrom foreign objects – Middle ear muscles may provide protection from loudMiddle ear muscles may provide protection from loud soundssounds  TransducerTransducer – Converts acoustic energy to mechanical energyConverts acoustic energy to mechanical energy – Converts mechanical energy to hydraulic energyConverts mechanical energy to hydraulic energy  AmplifierAmplifier – Transformer action of the middle earTransformer action of the middle ear – only about 1/1000 of the acoustic energy in air would beonly about 1/1000 of the acoustic energy in air would be transmitted to the inner-ear fluids (about 30 dB hearing loss)transmitted to the inner-ear fluids (about 30 dB hearing loss)
  11. Tympanic cavity • Volume – 1.5 ml • Form – flatten drum • Structure – six walls: - Lateral - Medial - Anterior - Posterior - Superior - Inferior
  12. Lateral wall
  13. Tympanic MembraneTympanic Membrane  Separates outer ear from middle earSeparates outer ear from middle ear  Barrier from foreign objectsBarrier from foreign objects  Cone-shaped in appearanceCone-shaped in appearance – about 17.5 mm in diameterabout 17.5 mm in diameter  Vibrates in response to soundVibrates in response to sound waves.waves.  The membrane movement isThe membrane movement is incredibly smallincredibly small – as little as one-billionth of aas little as one-billionth of a centimetercentimeter
  14. Two parts: Pars flaccida – upper, thin, loose Pars tensa – lower, tense Three layers: 1. Outer, cutaneous – continuation of the canal skin. No hairs and glands. 2. Middle, fibrous – elastic fibers. 3. Inner, mucous – tympanic cavity lining Tympanic membrane
  15. Most complex. On this wall are distinguished: -fenestra vestibuli -fenestra cochleae -promontorium -prominentia canalis semicircularis lateralis - prominentia canalis facialis Superior wall, paries tegmentalis Separates tympanic from cranial cavity. Children less than 2 years – infections of the middle ear can pass to the cranial cavity. Medial wall, paries labyrinthicus
  16. Inferior wall, paries jugularis Separates tympanic cavity from fossa jugularis Anterior wall, paries caroticus Separates tympanic cavity from canalis caroticus -canalis musculotubularis Posterior wall, paries mastoideus Composed of: •Styloid complex of Procter •Antrum mastoideum •Fossa incudis
  17. Auditory (Eustachian) tube Connects tympanic cavity with pharynx Two openings: •ostium pharyngeum tubae •ostium tympanicum tubae. Two parts: •bony •cartilagenous Function: • Equalizes pressure on both sides ofEqualizes pressure on both sides of tympanic membrane for optimal hearing.tympanic membrane for optimal hearing.
  18. OssiclesOssicles  MalleusMalleus (hammer)(hammer)  IncusIncus (anvil)(anvil)  StapesStapes (stirrup)(stirrup) smallest bonesmallest bone of the bodyof the body
  19. Inner EarInner Ear Auditory Vestibular Vestibular semicircular canals utricle and saccule Cochlear traveling wave traveling wave traveling wave pathologies
  20. Inner earInner ear Two compartments:Two compartments: ((аа) Bony labyrinth and) Bony labyrinth and (b) Membraneous labyrinth.(b) Membraneous labyrinth. Bony labyrinth:: •• complex cavity in dense bonecomplex cavity in dense bone ((pars petrosapars petrosa)) Parts of the bony labyrinth:Parts of the bony labyrinth: a.Vestibuluma.Vestibulum.. b. Semicircular canals.b. Semicircular canals. c.Cochleac.Cochlea..
  21. Bony labyrinth. Labyrinthus osseus Vestibulum and semicircular canals
  22. Vestibulum Two walls: External and internal. External wall has • Fenestra vestibuli. Internal wall has: •Recessus ellipticus •Recessus sphericus •Recessus cochlearis •Maculae cribrosae superior, medius, inferior
  23. Openings into vestibulumOpenings into vestibulum aa.. Fenestra vestibuli.Fenestra vestibuli. b.b. Fenestra cochleae.Fenestra cochleae. c.c. Openings (5) of the semicircular canalsOpenings (5) of the semicircular canals d.d. Aqueductus vestibuliAqueductus vestibuli
  24. 3: anterior, posterior and lateral. Have ampulla and crus. Canalis semicircularis lateralis –horizontal. - eminentia canalis semicircularis lateralis on the medial wall of tympanic cavity. Canalis semicircularis anterior –frontal. - eminentia arcuata on pars petrosa of os temporale. Canalis semicircularis posterior –sagittal Semicircular canals
  25. Cochlea Meatus acusticus internus Labyrinthus osseus. Cochlea
  26. • Cone-shaped: base and apex. • Canalis spiralis cochleae - promontorium, on the medial wall of tympanic cavity. • Modiolus - canales longitudinales modioli. • Lamina spiralis ossea -hamulus Divides canalis spiralis cochleae into: •Scala tympani •Scala vestibuli Охлюв
  27. Labyrinthus membranaceus
  28. Function of Inner EarFunction of Inner Ear  Converts mechanicalConverts mechanical sound waves to neuralsound waves to neural impulses that can beimpulses that can be recognized by the brainrecognized by the brain for:for: – HearingHearing – BalanceBalance
  29. •Closed system of sacs and ducts underling the bony labyrinth. •Filled with endolymph. •Two parts: vestibular & cochlear. Membraneous labyrinth. Labyrinthus membranaceus
  30. Vestibular labyrinth Composed of : • Two bags - sacculus et utriculus • Three ductus semicirculares • One ductus endolymphaticus.
  31. Cristra ampullaris
  32. BalanceBalance  Linear motionLinear motion  Rotary motionRotary motion
  33. Sensory cells (Epitheliocytus pilosus)
  34. Macula utriculi (sacculi) Otoliths. Statoconia
  35. MMaculaeaculae react to gravitational forcesreact to gravitational forces andand participate in maintaining the static balanceparticipate in maintaining the static balance .. Static balance
  36. CCristaeristae ampullares react to rotatory movementsampullares react to rotatory movements andand paticipate in dynamic balancepaticipate in dynamic balance .. Dynamic balance
  37. CochleaCochlea  The cochlea resembles aThe cochlea resembles a snail shell and spirals forsnail shell and spirals for about 2 3/4 turns around aabout 2 3/4 turns around a bony columnbony column  Within the cochlea areWithin the cochlea are three canals:three canals: – Scala VestibuliScala Vestibuli – Scala TympaniScala Tympani – Scala MediaScala Media
  38. Spiral canal - ductus cochlearis. Occupies scala media of the spiral canal. Has two blind ends - cecum vestibulare and cecum cupulare. Has three walls: • paries vestibularis • paries externus • paries tympanicus- organ of Corti, basal membrane Cochlear labyrinth
  39. Organ of CortiOrgan of Corti  End organ ofEnd organ of hearinghearing
  40. Organ of CortiOrgan of Corti
  41. Sensory cells of the organ of Corti