Audition Flashcards
What is the function of the external (outer) ear?
It collects sound waves and passes them inwards
What structures make up the external ear? Describe them if applicable
Auricle/Pinna- Cartilage covered with skin
External auditory canal/acoustic meatus
Tympanic membrane or eardrum-Skin and CT
True or False: The auricles of most animals are large and can be oriented in different directions?
True
What are the ear ossicles? (describe and name them)
Small bones in the tympanic cavity
Malleus, uncus, stapes
What is the function of the ear ossicles?
Transmit vibrations of the eardrum to the oval window
True or False: The functions of the ear ossicles are enhanced by the tensor tympani and the stapedius muscles?
False- They are dampened
What is the purpose of damping muscles?
CNS control over sensory input to protect the auditory receptor cells. Innervated by cranial nerves
What is the bony labyrinth?
Tortuous channels that go through the temporal bone
contain the vestibule, cochlea, and semicircular canals
Filled with perilymph
What is the membranous labyrinth?
Series of membranous sacs withing the bony labyrinth
Filled with endolymph- potassium rich fluid
What is the structure of the vestibule?
Central egg-shaped cavity of the bony labyrinth
Suspended in it’s perilymph are two sacs
What is the function on the sacs of the vestibule?
House equilibrium receptors called maculae
Respond to gravity changes and the position of the head
Describe the structure of the semicircular canals.
Three canals that each define two-thirds of a circle and lie in the three planes of space
Membranous semicircular ducts line each canal
The ampulla is the swollen end of each canal and it houses equilibrium receptors in the crista ampullaris
What are the three chambers of the cochlea?
Scala vestibuli
Scala media
Scala tympani
What is the cochlea?
A spiral, conical, bony chamber
It extends from the anterior vestibule
Coils around a bony pillar called the modiolus
Contains cochlear duct and the organ of corti
Where does the cochlear duct end?
Cochlear apex
What is the function of the organ of corti?
Hearing receptor
Where does the scala tympani terminate?
Round oval window
What are the scala tympani and the vestibuli filled with?
Perilymph
What makes the scala tympani and the vestibuli continuous with each other?
The helicotrema
What is the scala media filled with?
Endolymph
What is the floor of the cochlear duct composed of?
Bony spiral lamina
Basilar membrane
The cochlear branch of nerve VIII
What supports the organ of Corti?
Basilar membrane
Where does the cochlear brain of nerve VIII start and stop?
Organ of cori to the brain
What is the route of sound transmission in the outer ear
Pinna -> auditory canal -> eardrum
What is the route of transmission of sound to the inner ear?
Scales vestibuli and tympani -> cochlear duct
What is the route of sound transmission to the middle ear?
Malleus, incus, stapes to oval window
