Flashcards in Lecture 27 RH Deck (58)
What is the eardrum?
What is the middle ear?
space between tympanic membrane and petrous part of temporal bone is called the middle ear.
What is the inner ear?
Space within petrous part of temporal bone is the inner ear
What is the outer ear?
Before the tympanic membrane is the outer ear.
How is loss of balance controlled?
In the petrous part of the temporal bone is a portion that allows us to control balance.
What are the components of the outer ear?
auricle: cartilaginous and collects sound. Tragus is the flap anterior to the ear canal.
How is sound able to reach the middle and inner ear?
Sound is transmitted through external auditory meatus to the tympanic membrane.
What is the structure of the external acoustic meatus?
External acoustic meatus is supported laterally (lateral 1/3) by cartilage and medially by the temporal bone. It is lined by hairy skin and cerumen glands.
What is the function of cerumen?
prevents maceration of skin with water.
What does "maceration" mean?
Maceration is defined as the softening and breaking down of skin resulting from prolonged exposure to moisture.
What nerves supply the external auditory meatus?
Nerve supply to external auditory meatus is done via several nerves:
posterior+inferior by vagus
anterior +superior by auriculotemporal nerve (from V3 of trigeminal nerve)
Where are other locations that pain of the ear could be referred to?
Pain of ear could be referred to other locations that the mandibular division of the trigeminal nerve innervates. (eg teeth)
*Pain from teeth could be referred to the ear.
What is the indentation on the tympanic membrane called?
Indentation on the tympanic membrane formed by the malleus of the inner ear.
What shape does the tympanic membrane have?
tympanic membrane is concave laterally.
What causes the concavity seen in the tympanic membrane?
Concavity depends on pressure within the middle ear relative to the outer ear.
What is the cone of light of the tympanic membrane?
Cone of light can be seen at the antero inferior quadrant. If that light is not visible then that means the pressure difference is indicating a problem with the middle ear.
What is the epitympanic recess? What is the problem with it?
Communicates with mastoid air cells and so infection of nasal cavity and auditory tube can go to mastoid air sinuses.
What are the cavities of the middle ear?
middle ear is split up into 2 compartments:
Tympanic cavity proper (immediately medial to tympanic membrane)
Epitympanic recess: superior to the tympanic cavity.
How does the nose/mouth connect to the ear's tympanic cavity?
Pharynx is connected to the tympanic cavity in the ear via the auditory tube (aka pharyngotympanic tube)
What is pharyngotympanic tube made of?
Primarily cartilaginous with the exception of the tympanic cavity which is embedded in bone.
What direction does the pharyngotympanic tube point?
anteriorly and inferiorly
What is a problem that arises with having the pharyngotympanic tube between the nasopharynx and the tympanic cavity?
because of the downwards opening infection could travel between cavities
What is the problem of inflammation on the ear?
Inflammation causes ossicles to be interrupted and pressure increase could push out the tympanic membrane and potentially damage it.
What are ossicles?
ossicles are the smallest bones in the body. 3 types of these bones:
These bones articulate with each other.
How is sound heard?
sound vibrates tympanic membrane and this causes vibration of ossicles in the inner ear and this is transmitted from stapes to another membrane in the inner ear which in turn activates sensory nerves.
What is the difference between the auditory tube in adults and in children and the infection rates?
in children the auditory tube is shorter smaller and more horizontal. For this reason infection transfers more often in children than it does in adults. (more middle ear infection in children)
What is a potential complication of middle ear infection in children?
Chronic ear infections in infants could negatively influence language development.
What kind of muscles can be found in the ear? What is their function?
Ossicles are associated with several muscles that are attached to the walls of the middle ear and attach onto some of the ossicles. They dampen the amplitude of vibration of the bones and so they decrease the perceived loudness of the sound.
How is it that when we hear very loud that they become less loud to us over time?
A reflex arc attaches to muscles in the ear to decrease loudness of sound when required.