Anatomy W11 - The ear Flashcards
What components make up the external ear?
The auricle/pinna
The external acoustic meatus
What is the function of the external ear?
Gathers sounds and channels/transmits it through the external acoustic meatus
What cartilage forms the auricle?
Elastic cartilage
What epithelium lines the external acoustic meatus?
Stratified squamous keratinised epithelium
What are they safety measures that prevent foreign bodies entering the ear?
Ceruminous glands that produce wax
Little hairs at the start of the external auditory meatus
What is a clinical problem of the external ear?
How do you treat this?
Otitis externa - bacterial infection of the external auditory meatus which causes inflammation.
flush the ear out and give antibiotics
What epithelium lines the middle ear?
Respiratory epithelium - pseudostratified columnar epithelium with goblet cells
What is the tympanic membrane? - Where is it located?
(Also known as the eardrum)
Located in the middle ear
It’s a thin, tense membrane that transmits sound vibrations from the external acoustic meatus to the ossicles of the middle ear
Name the components of the middle ear.
The tympanic membrane
The ossicles - inca, malleus, stapes
The auditory tube
What is the function of the auditory tube in the middle ear?
Allows air into the middle ear
Why does new air have to be let in to the middle ear via the auditory tube?
Since the lining of the middle are absorbs the air
Where is the opening of the auditory tube?
In the nasopharynx - surrounded by the tubal elevation/tonsils
Name the ossicles of the middle ear.
Malleus - Handle connects to the tympanic membrane
Inca (between the malleus and stapes)
Stapes - looks like a stirrup and faces into the cochlear/internal ear
What joint is present between the ossicles?
Synovial joints
What holds the ossicles in place?
Ligaments
What is the ligament that holds the stapes in place called?
What clinical problem can be associated with this ligament?
The annular ligament of the stapes
Cause of deafness in older people:
This ligament can calcify with age = restricts movement of the stapes = deafness
What window does the stapes move in and out of?
The fenestra vestibuli / The oval window
Describe how the lever system of the ossicles functions.
As sound moves down the external acoustic meatus it causes movement/vibration of the tympanic membrane.
The vibration of the tympanic membrane cause the stapes to move in and out of the fenestra vestibuli
Movement of the fenestra vestibuli causes movement of fluid within the inner ear/cochlea which is received by the stereocilia/hair cells and transmits impulses down the vestibulocohlear nerve.
What is the function of the round window/fenestra cochleae?
Since fluid cannot be compressed within the inner ear/cochleae, when the stapes is in the fenestra vestibuli the fluid moves through the fenestra cochleae to compensate for this fluid movement.
What clinical problem can be associated with the middle ear? Describe what can occur.
Otitis media - infection of the middle ear /
Chronic otitis media - if it persists for a long time
Can lead to breakdown of the tympanic membrane = pus leaking out into the external acoustic meatus
Can also spread to the mastoid air cells = difficult to treat
What is the risk associated with a bad infection of the middle ear?
Facial palsy:
Since the bone separating the middle ear and the facial nerve is thin - infection can cause inflammation that applies presses to the facial nerve = palsy
Why is otitis media common?
Since the middle ear communicates with the nasopharynx via the auditory tube - infection can spread from the pharynx to ear easily.
What condition of the middle ear presents in young children around the age of starting school?
Chronic Otitis media with effusion
If you had to look at the tympanic membrane of a child with chronic otitis media with effusion with an auriscope, what would you see?
An air bubble and straw coloured mucous
