Auditory Flashcards
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Auditory Tube (Eustachian Tube)
- Definition: A canal connecting the middle ear to the nasopharynx (upper throat).
- Function: Equalizes air pressure on both sides of the tympanic membrane to maintain proper vibration for hearing.
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Tympanic Membrane
- Definition: Thin, cone-shaped membrane separating the outer ear from the middle ear.
- Function: Vibrates in response to sound waves and transmits those vibrations to the ossicles.
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External Acoustic Canal
- Definition: Tube running from the pinna to the tympanic membrane.
- Function: Directs sound waves toward the eardrum and protects the middle ear.
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Pinna (Auricle)
- Definition: External, visible part of the ear made of cartilage.
- Function: Collects and funnels sound waves into the external acoustic canal.
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Lobule
- Definition: The soft, fleshy lower part of the pinna.
- Function: Has no major auditory function; contains blood vessels and connective tissue.
Ossicles
- Definition: Three small bones in the middle ear that transmit sound vibrations from the tympanic membrane to the inner ear.
Malleus (Hammer)
- Definition: First ossicle attached to the tympanic membrane.
- Function: Receives vibrations from the tympanic membrane and transmits them to the incus.
Incus (Anvil)
- Definition: Middle ossicle between the malleus and stapes.
- Function: Transfers vibrations from the malleus to the stapes.
Stapes (Stirrup)
- Definition: Smallest bone in the body; connected to the oval window.
- Function: Transmits vibrations from the incus to the inner ear through the oval window.
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Oval Window
- Definition: A membrane-covered opening between the middle ear and the cochlea (specifically the scala vestibuli).
- Function: Receives vibrations from the stapes and transmits them into the fluid of the cochlea to initiate hearing.
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Round Window
- Definition: A flexible, membrane-covered opening between the middle ear and the cochlea (specifically the scala tympani).
- Function: Moves outward when the oval window moves inward, allowing fluid movement within the cochlea and preventing pressure buildup.
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Bony Labyrinth
exterior
Bony Labyrinth
- Definition: A rigid, hollow space within the petrous part of the temporal bone, filled with perilymph, that houses the membranous labyrinth.
- Parts:
1. Cochlea – involved in hearing
2. Vestibule – detects gravity and linear acceleration
3. Semicircular Canals – detect rotational (angular) head movements
Membranous Labyrinth
- Definition: A soft, flexible series of sacs and ducts suspended within the bony labyrinth, filled with endolymph and containing sensory receptors.
- Parts:
1. Cochlear Duct – located inside the Cochlea (for hearing)
2. Utricle and Saccule – located inside the Vestibule (detect gravity and linear acceleration)
3. Semicircular Ducts – located inside the Semicircular Canals (detect rotational head movements)
Cochlear Nerve
- Definition: A branch of the vestibulocochlear nerve (cranial nerve VIII) that carries auditory sensory information.
- Location: Connected to the Cochlear Duct of the membranous labyrinth, within the Cochlea of the bony labyrinth.
- Function: Transmits sound signals from the cochlea to the brain for auditory processing.
10 nervew fibers
Vestibular Nerve
- Definition: A branch of the vestibulocochlear nerve (cranial nerve VIII) that carries sensory information about balance and spatial orientation.
- Location: Connected to the Utricle, Saccule, and Semicircular Ducts of the membranous labyrinth, within the Vestibule and Semicircular Canals of the bony labyrinth.
- Function: Transmits signals related to head position and movement to the brain to help maintain balance.
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Semicircular Canals
- Definition: Three bony loops (anterior, posterior, lateral) in the bony labyrinth that detect rotational (angular) head movements.
- Contents: Filled with perilymph and house the semicircular ducts (part of the membranous labyrinth).
- Semicircular Ducts: Flexible tubes inside each canal, filled with endolymph, containing sensory receptors for detecting rotation.
1, 4 -> posterior and anterior semicircular canal
2 -> perilymph in semicircular canals
3, 5 -> posterior and anterior semicircular ducts
front
6 -> anterior semicircular canal
7 -> posterior cemicircular canal
8 -> lateral semicircular canal
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Ampullae
- Definition: Swollen, enlarged regions at the base of each semicircular duct within the membranous labyrinth.
- Location: Found inside the semicircular canals (of the bony labyrinth), where each semicircular duct expands.
- Contents: Contain the crista ampullaris, a sensory structure with hair cells that detect rotational (angular) head movements through the movement of endolymph.
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Crista Ampullaris
- Definition: Sensory structures located inside the ampullae of the three semicircular ducts (anterior, posterior, lateral), detecting rotational (angular) movements of the head.
- Location: One crista ampullaris is found in the ampulla of each semicircular duct, housed within the semicircular canals of the bony labyrinth.
- Components and Functions:
1. Hair Cells – Sensory receptors with stereocilia that detect bending caused by endolymph movement; initiate nerve signals.
2. Supporting Cells – Provide structural and metabolic support to the hair cells.
3. Cupula – Gelatinous structure that sits atop the hair cells; bends with endolymph movement, deflecting the hair cells.
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Planes and Associated Canals:
- Lateral (Horizontal) Semicircular Canal – Detects rotation in the horizontal plane (e.g., shaking head “no”).
- Anterior (Superior) Semicircular Canal – Detects rotation in the sagittal plane (e.g., nodding head “yes”).
- Posterior Semicircular Canal – Detects rotation in the coronal plane (e.g., tilting head toward shoulder).
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Vestibule
- Definition: The central part of the bony labyrinth between the cochlea and the semicircular canals.
- Contents: Contains the membranous structures called the utricle and saccule, which are filled with endolymph.
- Function: Detects gravity (static equilibrium) and linear acceleration (straight-line movements) through the maculae of the utricle and saccule.
1
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Saccule
- Definition: A small, membranous sac located within the vestibule of the bony labyrinth, part of the membranous labyrinth.
- Function: Detects vertical linear acceleration (e.g., moving up and down in an elevator) using the sensory structure called the macula.
- Key Point: Contains hair cells embedded in a gelatinous layer topped with otoliths (calcium carbonate crystals) that shift with head movement.
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Utricle
- Definition: A larger, membranous sac located within the vestibule of the bony labyrinth, part of the membranous labyrinth.
- Function: Detects horizontal linear acceleration (e.g., moving forward in a car) using the sensory structure called the macula.
- Key Point: Contains hair cells embedded in a gelatinous layer topped with otoliths (calcium carbonate crystals) that shift with head movement.
Maculae
- Definition: Sensory structures located inside the utricle and saccule that detect linear acceleration and head position relative to gravity.
- Location:
- Macula of the Utricle – Detects horizontal acceleration (e.g., moving forward in a car).
- Macula of the Saccule – Detects vertical acceleration (e.g., moving up and down in an elevator).
- Components and Functions:
- Hair Cells – Sensory receptors with stereocilia that detect movement of the otolithic membrane.
- Otolithic Membrane – Gelatinous layer that sits over the hair cells; moves in response to gravity and linear motion.
- Otoliths – Tiny calcium carbonate crystals embedded in the otolithic membrane; add weight and inertia, enhancing the membrane’s response to movement.
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Vestibular Duct (Scala Vestibuli)
- Definition: A perilymph-filled chamber in the cochlea, part of the bony labyrinth, located above the cochlear duct (scala media).
- Function: Receives pressure waves from the oval window and transmits them through the cochlea toward the apex, helping initiate movement of the cochlear duct for hearing.
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Tympanic Duct (Scala Tympani)
- Definition: A perilymph-filled chamber in the cochlea, part of the bony labyrinth, located below the cochlear duct (scala media).
- Function: Carries pressure waves from the apex of the cochlea toward the round window, where the waves are dissipated to relieve pressure within the cochlea.
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Cochlear Duct (Scala Media)
- Definition: An endolymph-filled chamber of the membranous labyrinth located between the vestibular duct (scala vestibuli) and tympanic duct (scala tympani) within the cochlea.
- Function: Houses the organ of Corti, the sensory structure responsible for detecting sound vibrations and converting them into nerve signals.
3
Vestibular Membrane
- Definition: A thin membrane that separates the vestibular duct (scala vestibuli) from the cochlear duct (scala media) inside the cochlea.
- Function: Helps maintain separation between perilymph (in the vestibular duct) and endolymph (in the cochlear duct), and transmits pressure waves from the vestibular duct to the cochlear duct.
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Basilar Membrane
- Definition: A flexible membrane that separates the cochlear duct (scala media) from the tympanic duct (scala tympani) inside the cochlea.
- Function: Supports the organ of Corti and vibrates in response to sound waves, with different regions responding to different sound frequencies, leading to activation of specific hair cells for auditory signaling.
