UNIT 6 - The ear = hearing & equilibrium Flashcards
structure of the outer ear
- auricle (pinna)
- External acoustic meatus
- Tympanic membrane
Auricle / Pinna
The visible fleshy structure on the side of head
External Acoustic Meatus
▪ Passageway that leads to the tympanic membrane
▪ The skin lining the passageway contains ceruminous glands which secrete cerumen, or earwax
- Earwax helps trap foreign debris and repel insects
Tympanic membrane
▪ Thin connective tissue membrane covered by epithelium that separates the outer & middle ear.
▪ Vibrates when sound waves strike it.
Structure of the middle ear
- Located whitin the tympanic cavity of the temporal bone
- Houses the ossicles
Ear Ossicles - three tiny bones in the middle ear cavity
Which ossicle is in contact with the tympanic membrane?
malleus
Which ossicle inserts into the oval window?
stapes
Ear Ossicles - Function - middle ear
together these transmit sound vibrations from the tympanic to the inner ear
Muscles of middle ear - Tensor & stapedius - middle ear
Function:
To reduce vibrations of the ossicles when they become excessive to minimize damage to hearing receptors
Oval window - middle ear
Membranous area that connects the stapes to a portion of the inner ear called the scala vestibuli
Round window - middle ear
▪ A flexible, membranous area between the middle ear cavity and the scala tympani of the cochlea.
▪ We will refer back to this in a few minutes to discuss its function.
Pharyngotympanic (Auditory) Tube - middle ear
- Passageway between the middle ear and the nasopharynx.
- Usually is flattened and closed but opens briefly with swallowing or yawning to equalize pressure between the atmosphere and the middle ear cavity.
Structure of the Inner ear
General structure:
▪ The inner ear is comprised of a bony labyrinth and a membranous labyrinth.
Bony Labyrinth - inner ear
▪ Series of connected chambers within the temporal bone which houses the inner ear structures and gives them their distinct shapes.
▪ Perilymph – fluid located in bony labyrinth and surrounding the membranous labyrinth
Membranous Labyrinth - inner ear
▪ Series of membranous tubes that generally follow the contours of the bony labyrinth and form the inner portions of the vestibule, semicircular canals, and cochlea.
▪ Endolymph – fluid located in membranous labyrinth.
Functional parts of inner ear
The functional parts of the inner ear include:
◦ vestibule
◦ semicircular canals
- Vestibular apparatus ( involved with equilibrium)
◦ cochlea
Structural features of the cochlea - inner ear
▪ Scala vestibuli – open space forming the upper 1/3 of each coil in the cochlea.
- Contains perilymph
Structural features of the cochlea - inner ear
▪ Vestibular membrane – separates the scala vestibuli from the cochlear duct.
Structural features of the cochlea - inner ear
▪ Cochlear duct – central, membranous portion of the cochlea; it houses the spiral organ (organ of Corti).
- Contains endolymph