Anatomy of the ear Flashcards
What are the basic functions of the ear?
Hearing
Balance
What are the parts of the ear?
External ear
Middle ear
Inner ear
What are the parts of the external ear?
Pinna
External auditory meatus
Lateral surface of tympanic membrane
What is the pinna made up of?
Cartilage
covered with skin
What are the parts of the pinna?
Helix
Antihelix
Concha
Tragus
Lobe
What is the helix of the pinna?
Outer fold of the pinna
What is the antihelix of the pinna?
Flat area deep to the helix of the pinna
What is the concha of the pinna?
Flat area deep to the antihelix of the pinna
What is the tragus of the pinna?
Flap over the external auditory meatus
What is the lobe of the pinna?
Most inferior part of the pinna
What is the lobe of the pinna made up of?
Loose adipose connective tissue
What is the external auditory meatus made up of?
Outer 1/3 is made up of cartilage
Inner 2/3 made up of bone
Both covered by skin
What skull bone makes up the inner external acoustic meatus?
Tympanic plate of temporal bone
What is the shape of the externa auditory meatus?
Sigmoid shape
How long is the external auditory meatus?
2.5cm
What does the cartilaginous part of the external auditory meatus contain?
Hairs
Glands producing wax
What are the functions of the hairs and wax in the external auditory meatus?
Physical barrier to prevent substances passing deeper into the external auditory meatus
Aid in migration of shed skin cells out of external auditory meatus
What is located at the end of the external auditory meatus?
The tympanic membrane
What does the tympanic membrane look like?
Translucent
What is the tympanic membrane made up of?
Fibrous connective tissue
What is the shape of the tympanic membrane?
Cone-shaped
apex points medially
What does the apex of the tympanic membrane attach to?
Malleus
What are the functions of the external ear?
Collect and transmit sound waves onto tympanic membrane
What is the middle ear made up of?
Ossicles
Air-filled cavity
Eustachian tube
What is another term for the middle ear?
Tympanic cavity
What skull bone contains the middle and inner ear?
Petrous part of temporal bone
What skull bone contains the internal acoustic meatus?
Petrous part of temporal bone
What are ossicles?
Small bones in the middle ear
How many ossicles are there?
Three
What does the malleus bone attach to?
Apex of tympanic membrane
Incus
What does the incus bone attach to?
Malleus
Stapes
What does the stapes bone attach to?
Incus
Oval window of cochlea
What are the three ossicles?
Malleus
Incus
Stapes
What type of joint connects the ossicle bones?
Synovial joints
What is the function of the ossicles?
Amplify vibrations from tympanic membrane
to oval window
What is the oval window?
Membrane-covered opening between the middle ear and inner ear
How do the ossicles amplify vibrations to the oval window?
By themselves vibrating
and hitting the oval window
Why is the function of the ossicles important?
Because the middle ear is filled with air, but the inner ear is filled with fluid
Poor conduction of sound from air to fluid
Ossicles in ear amplify vibrations to increase conduction of sound in fluid of inner ear
What does the degree of vibration of the ossicles depend on?
How loud the sound heard was
Which ossicle is in direct contact with the oval window?
Stapes
What is the acoustic reflex?
Loud sound heard
lots of vibration of stapes bone against oval window
contraction of stapedius muscle to reduce vibration of stapes
What part of stapes is in direct contact with the oval window?
Base plate
What controls the degree of vibration of the stapes ossicle?
Stapedius muscle contracts
to reduce vibration of stapes ossicle against oval window
What innervates the stapedius muscle?
Facial nerve
gives off branch to stapedius muscle
What is the eustachian tube?
Air-filled tube that runs from the middle ear cavity to the nasopharynx
What is the main function of the eustachian tube?
To equilibriate pressure in the middle ear cavity
with atmospheric pressure
What are the minor functions of the eustachian tube?
Ventilation of middle ear cavity
Drainage of mucus from middle ear cavity
Which cranial nerve runs close to the middle ear cavity?
CN7 facial nerve
What is the facial nerve passing through when it is close to the middle ear cavity?
Facial canal in petrous part of temporal bone
What is the relative pressure in the middle ear cavity?
Negative pressure
Why is there negative pressure in the middle ear cavity?
Because the mucous membrane lining the middle ear
continuously reabsorbs air from the middle ear cavity
Which cranial nerves run through the middle ear cavity?
Chorda tympani branch of CN7 facial nerve
CN8 vestibulocochlear nerve
What is the mastoid antrum?
Prolongation of middle ear cavity
What connects the middle ear to the mastoid antrum?
Mastoid aditus
What is the mastoid antrum continuous with apart from the middle ear?
Mastoid air cells
What are mastoid air cells?
Air-filled cavities within the mastoid part of the temporal bone
What skull bone contains the mastoid antrum?
Mastoid part of temporal bone
What is another term for the inner ear?
Labyrinth
What are the parts of the inner ear?
Cochlea
Vestibular apparatus
What is the cochlea made up of?
Fluid contained in cochlear duct
cochlear duct is lined by membrane
membrane is lined by bone
What covers the inner surface of the cochlear duct?
Spiral organ of Corti lines one surface
What is the spiral organ of Corti made up of?
Hair cells
have stereocilia on their apical domain
What happens in the cochlea when the oval window vibrates?
Fluid in cochlear duct moves
causes stereocilia on hair cells to move
generates action potentials
What carries action potentials from the cochlea?
Cochlear part of CN8 vestibulocochlear nerve
What information is carried in the cochlear part of the CN8 vestibulocochlear nerve?
Special sensory - hearing
Where does the cochlear part of the vestibulocochlear nerve carry action potentials to eventually?
Primary auditory cortex
in temporal lobe
What is the vestibular apparatus made up of?
Semicircular canals
Saccule
Utricle
What is a semicircular canal made up of?
Fluid contained in semicircular duct
semicircular duct is lined by membrane
membrane is lined by bone
What covers the inner surface of the semicircular ducts?
Hair cells
have stereocilia on their apical domain
What carries action potentials from the vestibular apparatus?
Vestibular part of CN8 vestibulocochlear nerve
What information is carried in the vestibular part of the CN8 vestibulocochlear nerve?
Special sensory - position, balance
What happens to the semicircular canals when the head is moved?
Fluid in semicircular canals moves
causes the stereocilia on the hair cells lining the semicircular canals to move
generates action potentials