Conference 26: temporal bone Flashcards
Which structure allows infection to spread from nasal cavity and pharynx to the middle ear cavity
auditory tube
Why do children get middle ear infections (otitis media) more often than adults?
- Their auditory tube is more horizontal
- Their auditory tube is shorter
- Children have weak immune systems
How is the Tympanic membrane oriented?
obliquely
slopes medially going posterior to anterior and going superior to inferior
Which are the longest walls of the tympanic membrane
anterior and inferior
What is the normal appearance of the tympanic membrane?
shiny, pearly gray and shaped like a funnel
What ossicle presses up against the tympanic membrane
malleus
What nerve innervates the mucosa of the middle ear cavity and is therefore is responsible for the pain felt during otitis media?
tympanic branch of the glossopharyngeal nerve
What is the roof of the middle ear cavity?
middle cranial fossa
floor of middle ear cavity?
internal jugular vein within the jugular foramen
lateral wall of the middle ear cavity?
- tympanic membrane
2. chorda tympani
medial wall of the middle ear cavity?
- facial nerve in facial canal
- oval window
- round window
- promentory
anterior wall of middle ear cavity?
Tensor tympani
auditory tube
carotid canal
what is conduction deafness?
deafness caused by interruption of the sound transmission into the inner ear (often caused by middle ear disease)
what could cause interruption of the ossicles conducting sound waves?
- fluid from infection
- tumor in middle ear cavity
- bone disease –> osteosclerosis
What is sensorineural deafness
deafness caused by lesion to the receptor (hair cells), vestibulocochlear nerve, or the terminus in the brain (low pons)
Describe the sound transmission pathway starting with sound waves entering the external auditory canal?
sound waves hit tympanic membrane and make it vibrate. the vibrating tympanic membrane starts the ossicles into motion and when the stapes is in motion it moves the oval window starting a fluid wave through the fluid of the cochlea. This fluid wave triggers hair cells and conducts an electrical signal to brain.
what does hyperacusis mean?
sounds appear louder than they really are
If a patient has hyperacusis, what 2 nerves could possibly be lesioned?
- facial nerve
2. V3
What are the two muscles that dampen loud noises
- stapedius
2. tensor tympani
How do these muscles dampen loud noises?
When the stapedius or tensor tympani contract they restrict movement of the ossicles
What do the skeletomotor fibers of the facial nerve innervate?
- stapedius muscle
- muscles of facial expression
- Stylohyoid
- Posterior belly of digastric
What kind of fibers are in the Chorda Tympani nerve?
- Taste
2. secretomotor
What do the secretomotor fibers of the facial nerve innervate?
- Lacrimal gland & palate and nasal cavity (via greater petrosal nerve)
- sublingual and submandibular glands (via chorda tympani)
What do the taste fibers of the facial nerve innervate?
anterior 2/3 of the tongue
What two fiber types have their cell bodies located in the geniculate ganglion?
taste and cutaneous sensation
both sensory fibers
What part of the skin does the facial nerve to cutaneous innervation to?
the skin over the mastoid process
