Middle Ear II

Question 1

What is the lateral malleolar ligament?

Answer 1

Extends from the neck of the malleus to the bony wall near notch of ravinus.

Question 2

What is the anterior malleolar ligament?

Answer 2

Extends from the anterior process of the malleus to the anterior or carotid wall of the middle ear cavity.

Question 3

What is the superior ligament of the incus?

Answer 3

Crosses from the body of the incus to the roof of the tympanic cavity just posterior to the superior ligament of the malleus.

Question 4

What is the posterior ligament of incus?

Answer 4

Courses from the tip of the short process to the fossa incudis.

Question 5

What is the annular ligament of the stapes?

Answer 5

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.

Question 6

What is the incudomalleal joint?

Answer 6

Malleus and incus are articulated by a diarthrodial (double saddle) joint.

Question 7

What is the incudostapedial joint?

Answer 7

An enarthroidal (ball and socket) joint considered to be immovable/slightly movable.

Question 8

What are pennate muscles? Where are they located? What kind of tissue are they made of?

Answer 8

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.

Question 9

What is the tensor tympani muscle? How large is it?

Answer 9

Larger of the tympanic muscles- 25 mm in length.

Question 10

What is the origin of the tensor tympani? What is the course? Insertion?

Answer 10

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.

Question 11

What innervates the tensor tympani?

Answer 11

Vth cranial nerve.

Question 12

What is the action of the tensor tympani?

Answer 12

Contractino pulls the malleus anteromedially, increases tympanic membrane tension, and stiffens ossicular chain and tympanic membrane.

Question 13

What is the cochleariform process?

Answer 13

The curved lateral terminal of the tensor tympani.

Question 14

Where is the tensor tympani’s tendon located?

Answer 14

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.

Question 15

How long is the stapedius muscle?

Answer 15

6mm

Question 16

What is the origin, course and insertion of the stapedius muscle?

Answer 16

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.

Question 17

What innervates the stapedius muscle?

Answer 17

Viith cranial nerve

Question 18

Where is the stapedius’ tendon located?

Answer 18

Enters tympanic cavity through a small opening at the apex of the pyramidal eminence on the posterior wall.

Question 19

What is the action of the stapedius?

Answer 19

Contracts to exert force on head of stapes rotating it posteriorly, and stiffening ossicle chain.

Question 20

Primary purpose of tympanic muscle?

Answer 20

Intensity control or protection (acoustic reflex).

Question 21

Which of two muscles is the key player? At what dB does it contract?

Answer 21

Stapedius. Elicited around 80-90 dB above threshold.

Question 22

What is the acoustic reflex?

Answer 22

Intensity control of protection from sound intensities well above the threshold of hearing.

Question 23

Is the ipsilateral or contralateral response stronger?

Answer 23

Ipsilateral.

Question 24

What is the acoustic reflex arc?

Answer 24

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.

Question 25

Tympanic muscles contribute to strength of _____.

Answer 25

Ossicular chain.

Question 26

What is the superior malleolar ligament?

Answer 26

Extends from the head of the malleus to the tegmen tympani. Holds head in recess.