Transcript 13anat1

Anatomy and Physiology
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Outer Ear
Middle Ear
Inner Ear
Central Auditory System
Vestibular System
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General Anatomical Terms
• Medial
– Towards the
midline
• Lateral
– Away from the
midline
• Superior
– Upper or above
• Inferior
– Lower or below
• Proximal
– Toward a
reference point
• Distal
– Away from a
reference point
• Anterior
– In front
• Posterior
– In back
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General Anatomical Terms
• Unilateral
– Same side
• Contralateral
– Opposite side
• Binaural
– Both ears
• Decussate
– Cross over
• Bilateral
– Both sides
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General Anatomical Terms
• Coronal Plane.
– In humans aka
frontal view
• Sagittal Plane.
– Side view
• Transverse Plane.
– Top or horizontal
view
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Cross Section
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Cross Section (outer ear)
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Cross Section (middle ear)
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Cross Section (inner ear)
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Cross Section
(central pathways)
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Temporal Bone
• Contains outer,
middle and inner
ears
• Articulates with
parietal, occipital,
frontal, and
sphenoid bones.
• Densest bone in
body
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Temporal Bone
• Squamous
Portion. Helps
enclose cranial
cavity.
• Mastoid Process.
Contains air cells.
• Zygomatic
Process. Forms
the zygomatic
arch. Connects
with zygomatic
bone.
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Temporal Bone
• Petrous portion (not shown). Located at the
base of the skull between the sphenoid and
occipital bones. Houses inner ear and
internal auditory canal (IAC connects inner
ear with brainstem). Levator palatini muscle is
attached to Petrous portion.
• Styloid Process (not shown). Located on the
medial/inferior portion of temporal bone.
Attaches to several pharyngial muscles.
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Outer Ear
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Outer Ear
• Pinna (auricle)
• External Auditory Meatus (ear canal)
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Outer Ear
• Pinna (auricle)
– Covered with skin and composed mostly of
cartilage with exception of the lobe.
– Temporalis muscle that is found posterior
and superior to pinna also helps secure
pinna.
– Sebaceous glands are found under skin.
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Pinna
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Pinna (concha)
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Pinna (photo)
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Pinna (helix)
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Pinna (helix)
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Pinna (lobe)
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Pinna (tragus)
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Pinna (scaphoid fossa)
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Pinna (triangular fossa)
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Pinna (anti-helix)
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Pinna (anti-tragus)
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Pinna (Darwin’s tubercle)
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Pinna (inter-tragal notch)
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External Auditory Meatus
(EAM)
• EAM is approximately 2.5 cm (1”) long
from entrance of concha to tympanic
membrane (TM) posterior-superior and
3.1 cm (1.2”) anterior-inferior.
• Slopes slightly downward from TM to
concha and is S shaped.
• Transverse view shows that EAM is
angled slightly forward.
• See next two slides to visualize.
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External Auditory Meatus
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External Auditory Meatus
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EAM (cartilaginous portion)
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EAM (osseous portion)
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EAM (sebacious &
cerumenous glands)
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EAM (isthmus)
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Function of Outer Ear
• Summary
– Collects sound and provides pathway
– Protects TM
– Keeps at a constant temperature and
humidity
– Helps us localize on vertical plane
– Resonates in high frequencies
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Function of Outer Ear
• Collects sound and provides pathway
– Because Concha is larger than TM the
outer ear acts like a funnel and slightly
increases SPL at TM.
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Function of Outer Ear
• Protects Tympanic Membrane
– S shape provides physical protection
– Cerumen and sweat lubricate EAM and help expel
debris.
– Hair follicles are tilted to concha discourage debris
from entering.
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Function of Outer Ear
• Keeps TM at a constant temperature
and humidity.
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Function of Outer Ear
• Localizes on Vertical Plane.
– Undulations and differences in cartilage of pinna
cause a sound shadow as well as
antiresonances between 6000-12000 Hz.
– These are important for front-back localization.
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Function of the Outer Ear
• Ear Canal Resonance
– EAM acts as a quarter wavelength
resonator.
– Resonance occurs at …
• EAM --- about 3400 Hz
• Concha --- about 5000 Hz
• Combined Effect --- about 2700 Hz.
– At 0 degrees azimuth gain is approximately
5 to 15 dB between 1500-5000 Hz. It is
slightly higher at 30 to 45 degrees azimuth.
– Differs for each individual.
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Function of the Outer Ear
• Head Related Transfer Function (EAM
resonance).
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Function of the Outer Ear
• Head Related Transfer Function (EAM
resonance).
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Summary
• Hit the Esc to return to index.
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