Middle Ear II Flashcards
What is the lateral malleolar ligament?
Extends from the neck of the malleus to the bony wall near notch of ravinus.
What is the anterior malleolar ligament?
Extends from the anterior process of the malleus to the anterior or carotid wall of the middle ear cavity.
What is the superior ligament of the incus?
Crosses from the body of the incus to the roof of the tympanic cavity just posterior to the superior ligament of the malleus.
What is the posterior ligament of incus?
Courses from the tip of the short process to the fossa incudis.
What is the annular ligament of the stapes?
The medial surface and the periphery of the footplate are covered by a thin layer of hyaline cartilage that is fastened to the bony wall of the oval window by this ligament.
What is the incudomalleal joint?
Malleus and incus are articulated by a diarthrodial (double saddle) joint.
What is the incudostapedial joint?
An enarthroidal (ball and socket) joint considered to be immovable/slightly movable.
What are pennate muscles? Where are they located? What kind of tissue are they made of?
Short fibers directed obliquely to impinge on a tendon at the midline. Can exert a lot of force due to way the fibers exert their force. Completely encased in bony canals, only tendons enter cavity. Made up of more elastic tissue which slows and dampens vibrations of ossicles.
What is the tensor tympani muscle? How large is it?
Larger of the tympanic muscles- 25 mm in length.
What is the origin of the tensor tympani? What is the course? Insertion?
The cartilaginous portion of the eustachian tube and greater wing of sphenoid bone. Courses posteriorly through canal for tensor tympani and around trochleariform process. Inserts into upper part of manubrium.
What innervates the tensor tympani?
Vth cranial nerve.
What is the action of the tensor tympani?
Contractino pulls the malleus anteromedially, increases tympanic membrane tension, and stiffens ossicular chain and tympanic membrane.
What is the cochleariform process?
The curved lateral terminal of the tensor tympani.
Where is the tensor tympani’s tendon located?
Emerges from orifice canal, making a sharp bend to conform to cochleariform process, and is then directed to its insertion on the upper part of the manubrium of the malleus.
How long is the stapedius muscle?
6mm
What is the origin, course and insertion of the stapedius muscle?
Origin is the bony canal running almost parallel to the facial nerve canal on the posterior wall of tympanic cavity. Courses anteriorly to insert on posterior neck of stapes.
What innervates the stapedius muscle?
Viith cranial nerve
Where is the stapedius’ tendon located?
Enters tympanic cavity through a small opening at the apex of the pyramidal eminence on the posterior wall.
What is the action of the stapedius?
Contracts to exert force on head of stapes rotating it posteriorly, and stiffening ossicle chain.
Primary purpose of tympanic muscle?
Intensity control or protection (acoustic reflex).
Which of two muscles is the key player? At what dB does it contract?
Stapedius. Elicited around 80-90 dB above threshold.
What is the acoustic reflex?
Intensity control of protection from sound intensities well above the threshold of hearing.
Is the ipsilateral or contralateral response stronger?
Ipsilateral.
What is the acoustic reflex arc?
Outer ear-middle ear-inner ear-VIIIth nerve- Ipsilateral cochlear nucleus-Ipsilateral superior olivary nucleus-VII and V nerves innervate stapedial and tensor tympani muscles to contract in both ears.
Tympanic muscles contribute to strength of _____.
Ossicular chain.
What is the superior malleolar ligament?
Extends from the head of the malleus to the tegmen tympani. Holds head in recess.
