Ear Week 3 FINISHED Flashcards
What is the ear also known as?
The vestibulocochlear organ
What are the 2 main functions of the ear?
Hearing
Equilibrium and balance
What is the ear divided into
External
Middle
Inner
Where are the structures relating to hearing and equilibrium located? How does the sound get there?
In the inner ear. The sound gets here by being transferred from the external and middle ear.
What separates the middle and outer ear?
The tympanic membrane
What joins the middle ear to the nasopharynx?
The pharygnotympanic tube
What are the 2 parts of the outer ear?
Auricle and external auditory meatus
What does the auricle do?
It aids in collecting sound
What does the external auditory meatus do?
Conducts the sound to the tympanic membrane
What does the auricle contain/what is it made of?
Mostly fibrocartilage covered in skin
What are the depressions in the auricle called?
The concha
What are the parts of the auricle? Explain each of the parts
The lobule - contains no cartilage, only fat, skin, connective tissue and vessels.
Tragus - projection of cartilage, anterior to EAM
Helix - outer curved fleshy ridge of the auricle
Scaphoid - boat shaped
What bone does the EAM lead through?
The temporal bone
How long is the EAM in adults?
2-3cm
Describe the lateral 1/3 of the EAM:
Lateral 1/3 is cartilage, lined with skin and is continuous with the auricle
Describe the medial 2/3 of the EAM:
The medial 2/3 is bone and lined with thin skin which is continuous with the tympanic membrane
What is the name for ear wax?
Cerumen
What is the function of cerumen?
Protects skin lining EAM
Water and insect repellant
Helps keep tympanic membrane pliable
Where is cerumen made?
Ceruminous glands in the subcutaneous tissues of the cartilaginous part of the EAM produce cerumen
What is the shape of the tympanic membrane?
Thin oval shaped, semitransparent membrane
1cm in diametre
What covers the external surface of the tympanic membrane?
Very thin layer of skin
What cover the inside of the tympanic membrane?
Internally covered by the mucous membrane of the middle ear
How does the tympanic membrane transmit sound?
The tympanic membrane moves in response to air vibrations from the EAM
Movements are then transmitted through the ossicles to the inner ear
Where is the middle ear found?
In the petrous part of the temporal bone
What does the middle ear include?
The tympanic cavity
The epitympanic recess
What are the contents of the middle ear?
Ossicles: the malleus, incus, stapes.
Muscles: Stapedius and tensor tympani
Chorda tympani nerve, a branch of the Facial nerve (CN VII) (provides taste fibres to the anterior 2/3 of the tongue, parasym to sublingual and submandibular glands
Tympanic plexus of nerves (formed by Facial and Glossopharyngeal nerves)
What do the ossicles do?
They form a chain across the tympanic cavity from the tympanic membrane to the oval window (which is the entrance to the middle ear)
What are the ossicles covered with?
Mucous membrane but not periosteum
Where does the tensor tympani arise?
Cartilaginous part of the pharyngotympanic tube
Greater wing of the sphenoid bone
Petrous part of the temporal bone
Where does tensor tympani insert?
Malleus
What is the function of tensor tympani and what is its nerve supply?
Dampens movements of the ossicles and tympanic membrane
Supplied by Mandibular nerve CN V (3)
What is the claim to fame of the stapedius muscle?
Smallest voluntary striated muscle in the body
Where does the stapedius arise?
Posterior wall tympanic cavity (temporal bone)
Stapes
What is the function of the stapedius and what is its nerve supply?
Prevents excessive movement of the stapes
Supplied by Facial nerve CN VII (nerve to stapedius)
What is the pharygnotympanic tube also known as?
The auditory tube or the eustachian tube
Which part of the eustachian tube is bone>
Lateral/ posterior 1/3
What is the eustachian tube made of excluding the bony part?
Cartilage
What is the eustachian tube lined with?
A mucous membrane, which is continuous with the tympanic cavity and nasopharynx
What is the function of the eustachian tube?
Equalises pressure in the middle ear with the atmospheric pressure
When is the eustachian tube usually closed?
All the time except when eating, yawning, chewing, swallowing etc
What opens the eustachian tube?
Levator veli palatini and tensor veli palatini (muscles of the soft palate)
What is the mastoid antrum?
An air filled extension of the middle ear. It is a cavity in the mastoid process of the temporal bone
What is in the floor of the mastoid antrum?
Has several apertures where it is continuous with the mastoid air cells
What lines the mastoid antrum and why is it clinically significant?
A mucous membrane which is continuous with the lining of the middle ear
What does the inner ear contain?
The vestibulocochlear organs
What part of the inner ear/temporal bone are the vestibulocochlear organs found?
Found in the petrous part of the temporal bone
What is the bony labyrinth?
A complex system of communicating cavities
What is suspended within the bony labyrinth?
The membranous labyrinth
What is the membranous labyrinth suspended within?
A fluid called the perilymph
What does the membranous labyrinth contain?
Endolymph
What are the fluids in the inner ear responsible for?
Involved in carrying sound wave to the end organs for hearing and balance
What are the 3 parts of the labyrinth?
A cave composed of 3 parts:
Cochlea
Vestibule (saccule & utricle)
Semicircular canals
What is the cochlear?
Latin for small snail
Concerned with the reception of sound
What is the vestibule?
Small oval chamber
Contains the saccule and utricle
Features the oval window on the lateral wall
Part of the balancing apparatus
What are the semicircular canals?
3 fluid filled bony loops
Part of the balance system
What is the internal auditory meatus? How long is it and where is it located?
A narrow canal, about one centimetre long and is contained within the petrous part of the temporal bone.
What is the IAM closed laterally by? What is it closed off from?
It is closed off from the internal ear by a thin perforated plate of bone
What passes through the bony plate that separates the IAM from the internal ear?
The facial nerve, the vestibulocochlear nerve and some blood vessels.
What happens to the vestibulocochlear nerve at the lateral end of the internal auditory meatus?
It divides into its 2 components to supply the various parts of the ear.
