Anatomy Of The Ear Flashcards
What makes up the external ear
Pinna and the external acoustic meatus
What is another name for the external acoustic meatus
Ear canal
Where does the external acoustic meatus end
The tympanic membrane
Role of the pinna
Collects sound waves and funnels them into the external acoustic meatus
What does the pinna attach to
The temporal bone
What is the external acoustic meatus formed from
Lateral 1/3 by cartilage
Medial 2/3 by temporal bone
What lines the external acoustic meatus
Stratified squamous epithelium
Role of ceruminous glands
Produce ear wax
What is used to examine the external acoustic meatus
Otoscope
How to move the pinna in an adult when using an otoscope
Pull auricle posteriosuperiorly
Arterial supply of the external ear
Branches of the external carotid artery
What is the tympanic cavity
Air-filled chamber in the petrous portion of the temporal bone which contains the apparatus for the middle ear
What are the 2 parts of the middle ear
Tympanic cavity proper and the epitympanic recess
What lines the middle ear
Columnar-lined mucosa
Innervation of the middle ear
Glossopharyngeal
What is the tegmen tympani
Thin plate of bone separating the tympanic cavity from the middle cranial fossa
What vein is closely related to the middle ear
Internal jugular vein
What is the mastoid aditus
Opening in the tympanic recess which opens into the air cells of the mastoid process
Role of the oval window
Receives footplate of the stapes
Role of the round window
Dissipates forces from the cochlear
What are the 2 main features of the anterior wall of the middle ear
Eustachian tube and chorda tympani
Name the 3 bones of the middle ear
Malleus, incus and stapes
What is the main function of the bones in the middle ear
Conduct vibrations of the tympanic membrane towards the inner ear
What connects the auditory ossicles
Synovial joints
Name the 2 muscles of the middle ear
Tensor tympani and stapedius
Where is the tensor tympani muscle located
Runs from the cartilaginous portion of the Eustachian tube to insert in the handle of the malleus
Function of the tensor tympani
Dampens sound by reducing vibrations of the tympanic membrane
Innervation of tensor tympani muscle
CN V3
Where does the stapedius muscle insert
Neck of the stapes
Role of the stapedius muscle
Dampens sound by reducing vibrations of stapes on oval window
Innervation of stapedius muscle
CN 7
Consequence of atmospheric pressure > tympanic pressure
Tympanic membrane pushes in reducing vibration of the ossicles
Consequence of atmospheric pressure < tympanic pressure
Tympanic membrane pushes out causing reduced vibration of ossicles
How do we adjust the ears to changes in atmospheric pressure
Palate muscles open the Eustachian tube to equalise the pressure
What is the Eustachian tube
Connection between the middle ear and the nasopharynx
Where is the Eustachian tube located
Posterior to the inferior nasal concha
What is the Eustachian tube made of
Posterior 1/3 bone, the rest is cartilage
Role of the Eustachian tube
Equalises pressure between the middle ear and the nasopharynx
Sensory innervation of the tympanic cavity mucosa
CN9 via the tympanic plexus
Role of the inner ear
Reception of sound and maintenance of balance
What is contained within the inner ear
Cochlear and vestibular apparatus
What is involved in the vestibular apparatus
Semicircular canals, utricle and saccule
Anatomical position of the inner ear
Deep within the petrous portion of temporal bone between the middle ear and the internal acoustic meatus
What are the 2 main components of the inner ear
Bony and membraneous labyrinth
What is the bony labyrinth of the inner ear
A fluid filled network series of bony cavities within the otic capsule
What is the membraneous labyrinth of the inner ear
A series of communicating ducts and sacs suspended within the bony labyrinth
What is the otic capsule
The dense bone of the petrous portion of the temporal bone that surrounds the membraneous labyrinth of the inner
What is the bony labyrinth filled with
Perilymph
What is the membraneous labyrinth filled with
Endolymph
What does the bony labyrinth consist of
Cochlea, vestibule and 3 semi-circular canals
What does the membraneous labyrinth consist of
Cochlear duct, semi-circular ducts, utricle and saccule
Where is the oval window located
Between the middle ear and the vestibule
What does the round window separate
The middle ear and the scala tympani
What is located within the vestibule
Saccule and utricle
What does the vestibule communicate with
Cochlea anteriorly and semi-circular canals posteriorly
Which part of the membranous labyrinth is responsible for hearing?
the cochlear duct
What are the two openings into the middle ear covered by membranes?
oval and round window
role of the ampulla in the semi-circular canals
contains sensory receptors that detect changes in the flow of endolymph, contributing to balance
How is the cochlear duct held in place within the cochlea?
by the spiral lamina
venous drainage of the inner ear
labyrinthine vein, emptying into the sigmoid sinus or inferior petrosal sinus
what innervates the inner ear
vestibulocochlear nerve
name the 3 semi-circular canals
anterior , lateral and posterior
what is responsible for balance
semi-circular ducts, utricle and saccule
anatomical location of the semi-circular ducts
superoposterior to the vestibule at right angles to each other
what is the membranous labyrinth surrounded by
perilymph
what is another name for the cochlear duct
scala media
what is the scala media
endolymph-filled cavity located within the bony scaffolding of the cochlea
what is the functional unit of the organ of corti
inner hair cell
where is the organ of corti located
on the basilar membrane within the cochlea
role of the organ of corti
converts sound vibrations into electrical signals for transmission through the cochlear nerve to the brain
where are hair cells of the vestibular apparatus located
maculae of the utricle and saccule, and the ampulla
where are the cell bodies for the neurones associated with vestibular hair cells found
within the vestibular ganglion
role of hair cells in the vestibular apparatus
detect head movement and acceleration, transmit signals to the brain, allowing for the processing of spatial orientation and motion
where are the cell bodies of the neurones associated with the organ of corti contained
within the spiral ganglion
what stimulates hair cells in the vestibular apparatus
the movement of endolymph
what do semi-circular canals detect
linear movement change
what does the anterior semi-circular canal detect
sagittal plane
what does the posterior semi-circular canal detect
coronal plane
what does the lateral semi-circular canal detect
axial plane
where does the vestibulocochlear nerve enter the inner ear via
internal acoustic meatus
name the 2 branches of the vestibular nerve
superior and inferior
what does the superior vestibular nerve supply
the lateral and anterior semi-circular ducts and the utricle
what does the inferior vestibular nerve supply
the posterior semi-circular duct and the saccule
route of the cochlear nerve within the inner ear
enters at the base of the modiolus and its branches pass through the lamina to supply the receptors of the Organ of Corti
what other nerve passes through the inner ear but does not innervate any of the structures
facial nerve
