Lecture 16 - Ear Flashcards
What are the divisions of the ear?
External, Middle, Internal
What is the function and description of the external ear?
- Visible part of ear -> tympanic membrane
- Contains cartilage
- Directs sound into the external acoustic meatus (ear canal)
What is the function of the ceruminous glands in the external ear?
Secrete a waxy substance (cerumen) that acts as a protective layer
What is the function of the tympanic membrane?
Vibrates in response to incoming sound waves
Describe the location and function of the middle ear
- Extends from the tympanic membrane to the inner ear
- Contains the auditory ossicles to transmit sound
List the three auditory ossicles
- Malleus (hammer)
- Incus (anvil)
- Stapes (Stirrup)
How to the ossicles transmit sound to the inner ear
Stapes vibrates against the oval window
What is the function of the round window? (Below to oval window)
- Assists in the transmission of sound waves through the inner ear
- Relieves pressure inside ear
What are the two muscles in the inner ear and what is their function?
Tensor tympani and Stapedius
- Stop the ossicles from vibrating too much
Describe the location and function of the euschatarian tube
- Air filled passageway that connects the pharynx and the middle ear
- Equalizes the pressure between the middle ear and the external environment
Describe features of the inner ear (4)
- Encased by the temporal bone
- Fluid filled
- Contains receptors for balance and hearing
- Innervated by branches of CN VIII (vestibulocochlear)
List the two fluid filled labyrinths in the inner ear
- Membranous labyrinth (inner)
- Bony labyrinth (outer)
List the three bony labyrinths
- Cochlea
- Vestibule
- Semicircular canals (3)
List the three membranous labyrinths
- Cochlear duct
- Utricle/Saccule (vestibule)
- Semicircular ducts
What is the function and general location of the Organ of Corti
- Located in the cochlear duct
- Contains hair cells that convert sound waves into electrical signals that are transmitted to the temporal lobe
Explain the transmission of sound via the Organ of Corti
- Waves in perilymph vibrate the basilar membrane
- Stereocilia of hair cells are pulled and pushed against the tectorial membrane (ceiling), as they bend electrical signals are generated
Summarize the process of hearing
Auricle -> Ear Canal -> Vibrates Tympanic Membrane -> Amplified by Ossicles -> Vibrates against oval window -> Vibration in perilymph -> Push against the basilar membrane of the cochlea -> Organ of Corti is moved and hair cells push up against tectorial membrane -> Electrical signal converted and sent to the temporal lobe through CN VIII
What three things do receptors in the vestibular apparatus detect
Rotation, gravity, acceleration
What are the semi-circular ducts filled with?
Endolymph
How is rotational movement detected by the ampullae?
Hair cells embedded in gelw - cupula - respond to movement
What are the two components of the vestibule? What are they filled with?
- Utricle and Saccule
- Endolymph
What are maculae, which is for horizontal acceleration and which is for vertical?
Found in the utricle and saccule
- Utricle macula - horizontal acceleration
- Saccule macula - vertical acceleration
How do the maculae detect movement
Otoliths (tiny crystals) sit on the top of gel, they weigh down the vestibule hair cells with movement (ex. tilting head down)
