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The “Ear” is housed within the TEMPORAL BONE

The “Ear” is housed within the TEMPORAL BONE. The Pinna - cartilaginous, highly variable in appearance, some landmarks. External Auditory Canal (or external auditory meatus) - 2.5 cm tube. The Outer Ear Consists of:. Pinna Landmarks. Helix Antihelix Concha Tragus Intertragal Notch

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The “Ear” is housed within the TEMPORAL BONE

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  1. The “Ear” is housed within the TEMPORAL BONE

  2. The Pinna - cartilaginous, highly variable in appearance, some landmarks. External Auditory Canal (or external auditory meatus) - 2.5 cm tube. The Outer Ear Consists of:

  3. Pinna Landmarks • Helix • Antihelix • Concha • Tragus • Intertragal Notch • Antitragus

  4. External Auditory Canal • lateral portion-cartilage • medial portion-osseous • lined with epidermal (skin) tissue • hairs in lateral part • cerumen (ear wax) secreted in lateral part.

  5. Outer Ear Functions • Amplification / Filtering • Protection • Localization

  6. The Middle Ear:A cleft within the temporal bone • Lining is mucous membrane • Tympanic Membrane separates it from EAC • Eustachian tube connects it to nasopharynx • Also Connected to Mastoid Air Cells

  7. Middle Ear Structures 1- Malleus 2- Incus --Ossicles 3- Stapes 4- Tympanic Membrane (Eardrum) 5- Round Window 6- Eustachian Tube

  8. Middle Ear Muscles 1.The StapediusAttaches to Stapes,Contracts in Response to Loud sounds, chewing, speaking; Facial (VIIth cranial) nerve 2. The Tensor TympaniHelps open Eustachian tube

  9. Middle Ear Functions • Impedance Matching • Filtering • Acoustic Reflex

  10. These sounds get through the middle ear most readily

  11. INNER EAR Two Halves: • Vestibular--transduces motion and pull of gravity • Cochlear--transduces sound energy (Both use Hair Cells)

  12. Within S. Media is the Organ of Corti

  13. The Stereocilia on IHCs and OHCs • OHCs (at top) • V or W shaped ranks • IHC (at bottom) • straight line ranks

  14. Cochlear Functions • Transduction- Converting acoustical-mechanical energy into electro-chemical energy. • Frequency Analysis-Breaking sound up into its component frequencies • Bekesy’s Traveling Wave • Active Tuning from OHCs

  15. Afferent & Efferent Neurons

  16. IHC activation alters firing rate

  17. Afferent neurons have their cell bodies in the Spiral Ganglion (4)

  18. Major Components of the Central Auditory Nervous System (CANS) • VIIIth cranial nerve • Cochlear Nucleus • Superior Olivary Complex • Lateral Lemniscus • Inferior Colliculus • Medial Geniculate Body • Primary Auditory Cortex <Trapezoid Body> Brainstem Mid-brain Thalamus Temporal Lobe

  19. AUDITORY CORTEX MEDIAL GENICULATE BODY INFERIOR COLLICULUS LATERAL LEMNISCUS SUPERIOR OLIVARY COMPLEX COCHLEAR NUCLEUS

  20. Mid-Saggital View of Brain 4th Ventricle Corpus Callosum Cerebellum Thalamus Pons

  21. Cortical Processing • Pattern Recognition • Duration Discrimination • Localization of Sounds • Selective Attention

  22. Cerebral Dominance/Laterality • Language Processing in the left hemisphere. (Remember the right ear has the strongest connections to the left hemisphere) • Most people show a right-ear advantage in processing linguistic stimuli

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