264

Front 1

AUDITORY OSSICLES

STAPES (STIRRUP)

Back 1

3. Stapes (stirrup)

a. Head: laterally directed, apical process; articulates with the lenticu-
lar process of the incus at the incudostapedial joint

b. Neck: constricted part adjoining the head
c. Crura: an anterior and a posterior crus extend from the neck to the
base; the anterior crus is shorter than the posterior crus

d. Base: flat, oval plate; attached to the margin of the oval window by
the annular ligament

Front 2

AUDITORY OSSICLES

-suspended where?
-mucosa, continous w/?

Back 2

4. The auditory ossicles are suspended within the tympanic cavity by deli-
cate ligaments; the mucosa lining the tympanic cavity ensheaths the
auditory ossicles and is also continuous with the mucosa lining the mas-
toid antrum, mastoid air cells, and auditory tube

Front 3

AUDITORY OSSICLES

CC: "incudo-malleolar & incudo-stapedial joints"

Back 3

5. Clinical note: since the incudomalleolar and incudostapedial joints are
synovial joints, they are subject to the same diseases, such as arthritis,
as other synovial joints

Front 4

TENSOR TYMPANI

OIAI

Back 4

1. Tensor tympani

a. Origin: the wall of the superior semicanal of the musculotubal canal

b. Insertion: its tendon bends laterally at a right angle over the coch-
leariform process to insert on the medial surface of the superior part
of the manubrium of the malleus

c. Action: contracts reflexly in response to loud sounds, and thus, ex-
erts a protective dampening effect by tensing the tympanic membrane
and reducing its sensitivity

d. Innervation: nerve to the tensor tympani, a branch of the nerve to
the medial pterygoid, which, in turn, is a branch of the mandibular
nerve

Front 5

STAPEDIUS

OIAI

CC: "FACIAL NERVE INJURY"

Back 5

2. Stapedius

a. Origin: the inner wall of the pyramidal eminence

b. Insertion: its tendon exits the orifice at the apex of the pyramidal
eminence and inserts on the posterior aspect of the neck of the stapes

c. Action: contracts reflexly in response to loud sounds, and thus, ex-
erts a protective dampening effect by holding the stapes against the
oval window

d. Innervation: nerve to the stapedius, a branch of the facial nerve

e. Clinical note: facial nerve injury and paralysis of the stapedius re-
sults in excessive acuteness of hearing or hyperacusia