speech mech chapter 9 part 2 Flashcards
Muscles of middle ear attached
to
ossicles
Smallest muscles of human body
Imbedded in posterior wall of middle ear
*Pulls stapes posteriorly
*tendon attaches to the neck of the stapes
*May aid in word recognition in noise by
attenuating low frequency components
of the noise
Stapedius muscle
Imbedded in posterior wall of middle ear
*Pulls stapes posteriorly
*tendon attaches to the neck of the stapes
*May aid in word recognition in noise by
attenuating low frequency components
of the noise
Muscles of middle ear attached
ossicles
Tensor tympani
*Inserts into upper manubrium malli
*Pulls malleus anteromedially
*inserts in the manubrium of the
malleus and contraction may cause the
TM to become tense
– Innervation of the Tensor tympani is via the
trigeminal nerve (Vth cranial nerve)
Both muscles stiffen
middle ear
transmission system
Reduce transmission of acoustical
information at
low frequencies to
protect against loud sounds
Unfortunately does not protect
against
high frequency sounds
common in modern industrial
society
Landmarks of medial wall of
middle ear cavity
– Oval window (fenestra ovalis)- footplate of
stapes is embedded in it
– Round window- entrance into scala tympani
of the cochlea
– Promontory of the cochlea
– Prominence of lateral semicircular canal
– Prominence of facial nerve
Eustachian tube (auditory tube)
– Responsible for aeration of middle ear
– Maintains equilibrium between
atmospheric pressure and middle ear
pressure for optimal sound transmission
– 36 mm in length
– The tube is normally kept closed, but is
opened by muscles in the nasopharynx
– Opening occurs during yawning,
sneezing, swallowing, or excessive air
pressure applied to the nose
Mastoid
– Honeycombed with hundreds of air cells
– The cells are lined with mucous
membrane similar to the middle ear
– The bony protuberance behind the
auricle is the mastoid process
* Used for placement of the bone oscillator for
hearing testing
* the mastoid process may extend to the floor
of the middle ear cavity
the inner ear contains sensors for balance which is
– The vestibular system
Osseous or bony labyrinth contains
inner ear structures
* Osseous vestibule
* Osseous semicircular canals
* Osseous cochlear labyrinth
* Membranous labyrinth
– Vestibule provides entrance to structures
the inner ear contains sensors for hearing which is called
The cochlea
osseous or bony vestibule Embedded within
petrous portion
of temporal bone
– The most dense bone in the body
Epithelial lining secretes perilymph
Fluid found within the superficial cavities of
the labyrinth
Oval window within
lateral wall
vestibular aqueduct within the
medial wall
vestibular contains three major recesses
– The spherical recess
– The cochlear recess
– The elliptical recess
Canals of the vestibular system Contain
sense organs for
movement of the body in space
– Responsible for sensation of movement of
the head in space
– 3 rings in right angles to each other
Anterior canals
sense movement of head
toward the shoulder
Posterior canals
sense movement of head
when nodding “yes”
Lateral semicircular canal
sense
movement of head when shaking head “no”
Osseous Cochlear
Labyrinth looks like
Looks like a coiled snail shell
– Wraps around 2 5/8 time before reaching
apex
modiolus
core of osseous labyrinth finely perforated bone
Parts of the labyrinth
– Entryway to the labyrinth
– The vestibule
– Semicircular canals
– Osseous cochlear canal
Divided by the osseous spinal
lamina into
– Scala vestibuli
– Scala tympani
– They contain perilymph
Vital structure attaches to scala
media
Houses sensory organ for hearing
The round window
Communicates between scala tympani and
middle ear
The oval window
Communicates between scala vestibuli and
middle ear space
Cochlear aqueduct
Small opening between the scala vestibuli
and the subarachnoid space of the cranial
cavity
Perilymph shares
the same composition as
cerebrospinal fluid (CSF) via the cochlear
aqueduct.
membranous labyrinth found
within the cavity of osseous
labyrinth
* Filled with fluid called endolymph
Vestibule or entrance to inner ear
– Contains cochlea – sense organ of hearing
– Contains semicircular canals – sense organs
of balance
Ampulla
expanded region of semicircular
canals near one opening to the vestibule
* Houses a crista ampularis- receptor organ for
movement
Ultricle and saccule
– Within vestibule (bony)
– House organs of vestibular system
Cochlear duct
– Between scala vestibuli and scala
tympani
– Make up intermediate scala media
– Houses sensory apparatus for hearing
Reissner’s membrane
thin
separation between the perilymph of
the scala vestibuli and the endolymph
of the scala media
Basilar membrane
“floor” of the
scala media that separates the scala
media from the scala tympani
*the organ of corti is on the basilar membrane.
Organ of Corti sensory organ of hearing is within the
inner ear
the organ of corti has four rows of hair cells that are
Supported by bed of Deiters’ cells
* Has three rows of outer hair cells (12,000 cells)
* Has a single row of inner hair cells (3,500 cells)
Tunnel of Corti
separate inner and outer
cells, product of pillars of Corti
Sterocilia (minute cilia) protrude from
surface of hair cells
Inner hair cells innervated by
many nerve
fibers
Outer hair cells innervated by
one nerve fiber
vascular supply is from
labyrinthine
Tectorial membrane
- Arises from spiral limbus
- Overlays hair cells
- Processes acoustic stimuli
