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Anat-The Ear
| Question | Answer |
|---|---|
| parts of the external ear | auricle (pinna), external acoustic meatus, tympanic membrane (eardrum) |
| function of pinna | channels sound waves into the ear canal |
| external acoustic meatus structure/location | ear canal through the temporal bone |
| tympanic membrane function | vibrates when energy is transferred from sound waves |
| middle ear parts | auditory (eustachian) tube, ossicles, oval window |
| middle ear structure/location/function | air-filled space in the temporal bone for hearing |
| auditory tube location | opens into the pharynx (throat) |
| auditory tube function | allows equalization of pressure by keeping the pressure in the middle ear cavity similar to that outside of the head so the eardrum doesn't rupture |
| three ossicles | malleus (hammer), incus (anvil), stapes (stirrup) |
| attachment points of ossicles | malleus connects to the eardrum and stapes occupies the oval window (like a piston/plug); connected by synovial joints |
| ossicles function | transmit vibrations |
| oval window structure | opening between the stapes and the inner ear |
| inner ear location/structure/function | completely embedded in the temporal bone, fluid-filled (lymph), for hearing and balance |
| bony (outer) labyrinth location/structure | in contact with bone tissue of the temporal bone- conforms to the shape of the cavity in the bone, like a maze of tubes |
| parts of the inner ear | cochlea, vestibule, semicircular canals |
| inner ear structure for hearing | cochlea |
| inner ear structure for balance | vestibule and semicircular canals |
| endolymph location | in the membranous labyrinth |
| perilymph location | fills the space between the membranous and bony labyrinth |
| parts of membranous labyrinth of cochlea | scala vestibuli,scala tympani, cochlear duct |
| parts of the cochlea filled with perilymph | scala vestibuli, scala tympani |
| parts of the cochlea filled with endolymph | cochlear duct |
| membranous labyrinth location/structure | found within the bony labyrinth; membrane-lined, fluid-filled tubes, sacs, and spaces |
| spiral organ (organ of Corti) parts | hair cells, tectorial membrane, basilar membrane |
| spiral organ function | cochlear structure responsible for hearing |
| hair cells structure/function | have projections called stereocilia (form of microvilli); sensory receptors of the inner ear that release neurotransmitter molecules based on the bending of the stereocilia |
| tectorial membrane location/structure | sits on top of the hair cells; stereocilia are embedded in it |
| basilar membrane location/function | at the bottom of the spiral organ; moves in response to sound waves to cause distortion of the stereocilia |
| cochlear nerve function | carries stimulus from the hair cells (produced by the bending of stereocilia) away from the cochlea |
| function of vestibule | evaluates the position of the head relative to gravity (stationary position) and detects linear acceleration and deceleration (linear movement) |
| two parts of the vestibule | saccule, utricle |
| maculae structure/location | contains hair cells embedded in an otolithic membrane which contains otoliths |
| utricle and saccule structure/function | two sacs that make up part of the membranous labyrinth in the vestibule; each contains a maculae |
| otolith structure/function | dense, little particles that provide mass for the otolithic membrane to make it sensitive to gravity (make gravity more likely to move the membrane) |
| vestibular branch of CNVIII function | carries the balance information away from the stimulated hair cells of the macula in the vestibule |
| semicircular canals function | evaluates rotational/angular movements of the head (angular acceleration and deceleration) |
| semicircular canals structure | three loops going in different directions; each has an ampullae at its base |
| structures of the membranous labyrinth of the semicircular canals | ampulla, crista ampullaris, hair cells, cupula |
| ampullae structure/function | swollen part at the base of each semicircular canal, contains the cells that give directional information |
| crista ampularis structure | elevated region of the ampulla that is covered by an epithelium of hair cells |
| cupula structure/function | gelatinous dome in which the hair cells of the crista ampullaris are embedded |
| destination of stimulus from the semicircular canals | vestibular branch of CNVIII (vestibulocochlear nerve) |
| mechanism of balance in the vestibule | moving the head causes the otolithic membrane to sag under the mass of the otoliths and the force of gravity and causes the stereocilia of the hair cells to bend |
| mechanism of balance in the semicircular canals | rotation of the head causes the endolymph surrounding the cupula to move in a direction opposite that of the head (due to inertia) which pushes against the cupula and causes the stereocilia in it to bend and create a stimulus in the hair cells |