major areas of the ear
outer, middle, inner
what fills most of the spaces of the ear, and why?
air because sound is an air-borne vibration
major areas of the outer ear
pinna, external auditory meatus, tympanic membrane
made of elastic cartilage covered with skin; gathers up air borne sound waves and points them down to the external auditory meatus
external auditory meatus
air-filled tube that leads down in an S-shape (for protection) to the tympanic membrane
made of connective tissue; vibrations hit here and the energy is collected and transferred to it, causing it to vibrate; must be thin for effective responsiveness; interface between outer and middle ear
major areas of the middle ear
tympanic cavity, ossicles, tensor tympani, stapedius, and eustachian tube
a hollow, air-filled space in temporal bone
what would happen if the tympanic cavity weren't hollow?
the membrane wouldn't be able to vibrate
the exit point whose terminus lies inside the mouth, allowing for air pressure equalization on either side of the membrane
what is the problem with where the eustachian tube terminates?
the mouth harbors a lot of bacteria, who can crawl up the eustachian tube to the tympanic cavity to grow
what is the solution to the problem of where the eustachian tube terminates?
a sphincter in the oral cavity that remains closed until air pressure needs to be changed
what are the ossicles of the middle ear?
malleus, incus, stapes
articulates vibrations between the tympanic membrane and the incus
articulates vibrations between the malleus and the stapes
what do the ossicles do, collectively?
transmit and mechanically amplify vibrations
what do the muscles of the middle ear do?
they contract to subdue the vibrations of the ossicles and lower volume of sounds
the physical space in the temporal bone for the inner ear
what makes up the bony labyrinth?
semicircular canals, vestibule, cochlea
3 loops at right angles to each other separated into superior, posterior and lateral
the big structure adjacent to the semicircular canals that houses the oval window
the snail-shaped structure of the inner ear containing the round window and cochlear duct
the membrane-enclosed spaces inside the bony labyrinth
what makes up the membraneous labyrinth?
semicircular ducts, utricle, saccule, cochlear duct
what fills the membraneous labyrinth?
what fills the bony labyrinth?
what is the point of the endolymph and perilymph?
equalize pressure because they're incompressible
area of ducts that contain gel-covered hair cells that move when you move to help with balance; little bulges at the base of the ducts
what is the function of the semicircular ducts?
the maintenance of body position in response to angular movement (acceleration and deceleration)
utricle and saccule
structures inside the vestibule of the inner ear (U connects to canals and S connects to cochlear duct) containing hair cells and otoliths
solid structures in the utricle and saccule that sink to the bottom, stimulating the hair cells that it lands on; always point down
endolymphatic duct and sac
connect the utricle and saccule
what is the function of the utricle and saccule?
orientation of the body in respect to gravity
name the layers of the interior cochlea from top to bottom
scala vestibuli, cochlear duct, tectorial membrane, organ of corti, basilar membrane, scala tympani
organ of corti
structure sitting on the basilar membrane of the cochlear duct and is responsible for detecting sound and converting mechanical vibrations into AP
what innervates the membraneous labyrinth at all parts?
describe a simplified hearing pathway
sound waves enter the pinna, travel to the external auditory meatus, and hit the tympanic membrane. The vibrations from the tympanic membrane are transferred to the malleus, then the incus, and then the stapes; here, the volume is adjusted. The stapes then vibrates against the oval window, which pushes at the perilymph, which then does 2 things: first, it pushes out the round window to relieve the pressure; then, it pushes on the endolymph, which pushes on the organ of corti, which detects this and converts the vibration to AP to send to the vestibulocochlear nerve. The nerve takes the AP to the medulla oblongata, then the inferior colliculus, then the thalamus, and finally, the temporal lobe for processing