HUBS1107 Lecture Notes - Lecture 6: Petrotympanic Fissure, Stylomastoid Foramen, Foramen Lacerum
26 Oct 2018
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Department
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Professor
A complex bone on lateral side of skull
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Has a petrous (rock-like/hard) and squamous part
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It articulates with mandible
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Petrotympanic fissure
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Stylomastoid foramen
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Foramen lacerum (usually packed with cartilages and
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blood vessels)
Carotid canal (provides blood to inside of skull)
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Jugular foramen (drains blood from the skull)
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Lots of holes (foramina) in temporal bone:
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Organs of hearing
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The vestibulocochlear nerve (CN VIII)
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The facial nerve (CN VII)
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Glossopharyngeal nerve (CN XI)
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Communicates with the nasopharynx
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Contains or transmits several important structures:
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Temporal Bone: General
Divided into external, middle and inner ear
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Ear: Gross Anatomy
Where the jaw sits and
articulates with temporal
bone
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Mandibular fossa:
Where the blood enters into the skull
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Carotid canal:
Where blood is drained from skull
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Jugular fossa:
The Ear and Temporal Bone
Saturday, 2 September 2017
3:54 PM
HUBS1107 Page 7.1
If sound is coming from up/down, the irregular shape of
external ear shapes the sound differently depending on if it is
coming from up/down
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Therefore, hearing is being processed by cartilaginous
auricles - localize where sound is coming from
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Concentrate sound waves and help localization (to tell which way
sound is coming from)
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Elastic cartilage directed slightly forward
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We have muscles that can move pinna
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Auricles (pinnas)
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Remnant of first gill arch in temporal bone
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In living, the outside third formed by cartilage
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Shape amplifies sound by 10 - 15 dB
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Innervated by CN IX glossopharyngeal and CN X Vagus - gag reflex
in response to bug in meatus
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External auditory meatus
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Border between external and middle ear
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Slightly concave and attached to malleus bone
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Transduces (converts) pressure waves in the air (sonic vibrations)
into mechanical vibration (movement of ossicles)
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Trivia - Brownian motion, normal excursions only tens of
nanometers
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Tympanic membrane (ear drum)
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External:
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Lies at junction of squamous and petrous part of temporal bone
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Air filled space that communicates with inner ear - helping with equalizing ear
drum
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External auditory meatus (tympanic membrane)
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If tube is blocked (due to nose blocks), air from outside can get into
space of tube and behind ear drum. Pressure inside the tube
increases and membrane of tube will bulge out - membrane of tube
can break or perforate. Equalization won't be able to occur
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Same applies when on plane with cabin pressure decreases
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Auditory tube communicates with nasopharynx
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Two tubes that communicate with outside world (potential trouble)
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Mastoid air cells makes the middle ear light as it is filled with air
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Disadvantage of cells filled with air is it's prone to infections
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Posterior wall communicates with mastoid air cells (filled with air)
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Oval and round windows on complex medial wall
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Ossicles: stapes, incus, malleus
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Muscles: stapedius, tensor tympani
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Contains three ossicles, two muscles, & chorda tympani nerve
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Joints of ossicles are synovial fluid joints - this means it's prone to
arteritis
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Can get joint inflammation, reducing the movement of the joints; can get
conductive hearing loss as a result
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Ossicles impart a mechanical advantage
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Muscles dampen forces
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Middle ear and its connections
Lies in the petrous portion of the temporal bone
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Membranous labyrinth suspended in a bony labyrinth
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Membranous labyrinth contains the sensory organs of balance and hearing
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Balance (Vestibular: semicircular canals and otolith organs)
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Hearing (Cochlea)
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Contains organs of:
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Transmits information about head position with respect to gravity and
acceleration of head in space
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Hair cells associated with otolith organs and semicircular canals convey
information via vestibular branch of CN VIII to vestibular nuclei in
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Vestibular system
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Inner ear
Inner
Middle
Tensor tympani - muscle that tenses tympanic membrane by pulling on malleus
This stops bone movements if there is loud sounds associated with movement of tympanic membrane -
reflex mechanism to loud sounds
Stapedius - muscle attached to stapes; it helps in reducing motion of ossicles associated with loud
sounds
Chorda tympani - facial nerve that passes through and goes into the anterior 2/3 of tongue
The auditory tube of children is more horizontal -
meaning they don't have gravity to help in
clearing any debris or gunk in the tube
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With children, the gunk and debris will remain in
the tube and as a result, can develop ear
infections
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If infection stays a long time, the cells of lining in
area will change from 80% ciliated cells and 20%
goblet cells to 80% goblet cells and 20% ciliated
cells
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Would require an insertion of grommet to drain
out the fluid from the infection
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Glued ear with children:
Stapes
Incus
Malleus
Tensor tympani
Chorda tympani
Stapedius
Tympanic membrane
HUBS1107 Page 7.2
Document Summary
A complex bone on lateral side of skull. Foramen lacerum (usually packed with cartilages and blood vessels) Carotid canal (provides blood to inside of skull) Where the jaw sits and articulates with temporal bone. Concentrate sound waves and help localization (to tell which way sound is coming from) If sound is coming from up/down, the irregular shape of external ear shapes the sound differently depending on if it is coming from up/down. Therefore, hearing is being processed by cartilaginous auricles - localize where sound is coming from. Remnant of first gill arch in temporal bone. In living, the outside third formed by cartilage. Shape amplifies sound by 10 - 15 db. Innervated by cn ix glossopharyngeal and cn x vagus - gag reflex in response to bug in meatus. Transduces (converts) pressure waves in the air (sonic vibrations) into mechanical vibration (movement of ossicles) Trivia - brownian motion, normal excursions only tens of nanometers.
