Case 4 Flashcards
What is a name for the outer ear?
Auricle
where is the middle ear cavity located?
Petreous part of the temporal bone
What type of cartilage makes up the auricle?
Elastic
What arteries supply the auricle?
Posterior auricular and superficial temporal
What part of the s-shaped E.A.M is cartilagenous?
lateral 1/3 is cartilagenous
medial 2/3 is bony
What is another name for earwax?
Cerumen
What part of the E.A.M. secretes cerumen?
Lateral cartilaginous 1/3
What covers the tympanic membrane externally and internally?
Skin externally, and mucous membrane internally
What provides the auricle sensory innervation?
The auriculotemporal branch of the mandibular nerve (V3) and auricular branches of the vagus nerve
Which bone attaches to the tympanic membrane what is the concavity caused by this attachment called?
The malleus (by its handle) the concavity produced is called the umbo.
What is the eardrum attached to?
The tympanic part of the temporal bone by a periphery of a fibrocartillaginous ring.
What does the lateral process of the malleus form at the tympanic membrane?
Anterior and posterior malleolar folds
What are the areas above and below the anterior and posterior malleolar folds respectively?
The pars flaccid and the pars tensa
What provides innervation to the outer surface of the tympanic membrane?
Mostly the auriculartemporal branch of mandibular (V3), but also the facial (VII) and Vagus (X) nerves
What provides sensory innervation to the inside of the tympanic membrane?
The glossopharyngeal nerve (IX)
what is the roof of the middle ear called?
Tegmental?
What bone separates the roof of the middle ear and the M.C.F dura
Tegmen tympani
What are the two main parts of the cavity of the middle ear?
The tympanic and epitympanic cavities.
What is the area above the level of the tympanic membrane?
epitympanic recess (attic)
What is the floor of the middle ear called and what is below the floor?
Jugular floor, and the superior bulb of the internal jugular vein is below the floor.
What is the posterior wall of the middle ear called?
Mastoid
What is just posterior to the epitympanic recess of the middle ear?
The auditus leading to the mastoid antrum
Why can infections of the middle ear easily spread to the mastoid area?
Because the mucous membrane of the mastoid is continuous with that of the middle ear.
What is the medial wall of the middle ear called?
Labyrinthe
What is the rounded bulge on the medial wall of the middle ear called? and what is associated with this bulge?
promotory, and the tympani plexus is associated with this bulge.
What is the lateral wall of the middle ear called?
Membranous
What is the anterior wall of the middle ear called?
Carotid
What is on the superior surface of the anterior wall of the middle cavity?
Opening for the pharyngotympanic tube.
What is the role of the eustation tube?
To equalize the pressure either side of the tympanic membrane.
What is the eustation tube surrounded by?
The third closest to the middle ear is surrounded by bone the two thirds closest to the nasopharynx by cartilage.
Where does the eustation tube enter the nasopharynx?
just posterior to the inferior meatus of the nasal cavity.
What provides arterial supply of the eustation tube?
The ascending pharyngeal artery ( a branch of the external carotid) the middle meningeal artery and the artery of the pterygoid canal (branches of the maxillary artery)
What provides venous drainage for the pharyngotympanic tube?
The pterygoid plexus off the veins in the infratemporal fossa.
The do the three bones of the middle ear form?
The osseous chain
where is the enlarged body of the incus found?
in the epitympanic recess.
Which of the muscles of the middle ear is larger - tensor tympani or stapedius?
The tensor tympani
What is the origin and insertion of the tensor tympani muscle?
It originates from the cartilaginous part of the eustation tube the greater wing of the sphenoid and it passes through its canal and ends at the upper part of the handle of malleus.
What innervates the tensor tympani muscle?
The mandibular branch of the trigemnal nerve (V)
What effect does contraction of the tensor tympani have on the ear what function does this serve?
Contraction of the tensor tympani pulls the head of the malleus medially making the tympanic membrane tenser reducing the force from vibrations in loud noices this protects the ear from damage as a result of loud noises.
Where does the stapedius muscle originate from? where does it insert?
it originates from the pyramidal eminence ( a small projection on the mastoid wall) and inserts into the posterior surface of the neck of the stapes.
What innervates the stapedius muscle?
a branch of the facial nerve (VII)
What is the effect of the contraction of the stapedius muscle what purpose does this serve?
It pulls the stapes posteriorly preventing excessive oscillation protecting the ear from damage caused by loud noises
What is the bony labyrinth what is contained within it?
The bony labyrinth is the series of bony cavities contained in the inner ear within these is the are a group of membranous ducts and sac known as the membranous labyrinth
what forms the medial border of the inner ear?
The internal acoustic meatus.
Where are the labyrinths of the inner ear located?
In the petrous part of the temporal bone.
What are the three parts of the bony labyrinth what lines them and what fluid are they filled with?
The vestibule, the three semicircular canals and the cochlea. They are lined with periosteum and contain a clear fluid called perilymph.
What are the parts of the membranous labyrinth? What are these membranous spaces filled with?
The semicircular ducts, the cochlear duct and the two sacs the utricle and the saccule. they are filled with endolymph
What part of the ear is the organ for hearing?
The cochlear
What are the organs for balance in the ear?
The utricle and the saccule
What is the central column of bone of the cochlea?
The modiolus.
What is the lamina of bone that spans the length of the modiolus called?
lamina of modiolus or osseous spiral lamina
What does the osseous spiral lamina attach to?
Basilar membrane
What are the three tubes of the cochlear coiled side by side one another in the cochlea?
The scala vestibuli, the scala media and the scala tympani
What separates the scala vestibuli and media?
the reissner’s membrane/ vestibular membrane
Why might the scala vestibuli and media be considered a single chamber?
The reissner’s/vestibular membrane is so thin and easily moved it does not obstruct the passage of sound.
What separates the scala media and the scala tympani?
The basilar membrane.
What lies on the basilar membrane?
The organ of corti.
What are the electromechanically sensitive cells within the organ of corti?
hair cells
Where do sound vibrations enter the cochlea what chamber are they passed into?
They pass through the oval window into the scala vestibuli.
How do the basilar fibres vary as you move further away from the oval window how does this effect their stiffness?
They vary from being about 0.04mm to .5mm in length and as the length increases their diameter decreases this results in their overall stiffness decreasing 100 fold.
Which basiliar fibres are best for what frequencies?
The short thick fibers near the oval window are best for high frequencies and the long flexible fibers are best for low frequencies.
What fibres are present in the pars tensa part of the tympanic membrane?
circular and radial