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Front 1

MIDDLE EAR

TYMPANIC MEMBRANE
-fxn
-"gaseous compression & rarefaction"

-vibration of malleus

Back 1

6. Function

a. Sound consists of alternating waves of gaseous compression and rar-
efaction; since compressed gas has a higher pressure than rarefied
gas, alternating changes in air pressure cause the tympanic mem-
brane to vibrate

b. Vibration of the tympanic membrane vibrates the malleus, which, in
turn, vibrates the incus and then the stapes; through the movements
of the auditory ossicles, sound vibrations are transmitted from the
tympanic membrane across the tympanic cavity to the fluid of the
inner ear

Front 2

TYMPANIC CAVITY

-describe
-roof

Back 2

B. Tympanic cavity

1. Slitlike, air-filled, mucosal-lined space medial to the tympanic membrane;
contains the auditory ossicles

2. Roof: separates the tympanic cavity from the middle cranial fossa; com-
posed of the tegmen tympani, a thin plate of the petrous part of the tem-
poral bone

Front 3

TYMPANIC CAVITY

-floor

Back 3

B. Tympanic cavity

3. Floor: formed by the jugular fossa, a smooth depression roofing the jugu-
lar foramen; the tympanic branch of the glossopharyngeal nerve arises
below the jugular foramen, enters the external opening of the tympanic
canaliculus between the carotid canal and jugular foramen, traverses the
tympanic canaliculus, and emerges through the internal opening of the-
tympanic canaliculus on the floor of the tympanic cavity

Front 4

TYMPANIC CAVITY

-anterior wall
-"carotico-tympanic nerves"

Back 4

B. Tympanic cavity

4. Anterior wall

a. Separates the tympanic cavity from the carotid canal; the carotico-
tympanic nerves, postganglionic sympathetic fibers from the inter-
nal carotid plexus, enter the tympanic cavity through its anterior wall

Front 5

TYMPANIC CAVITY

-anterior wall
-"musculotubal canal"

Back 5

B. Tympanic cavity

4. Anterior wall

b. Superiorly, the anterior wall presents the musculotubal canal, which
is divided into two parallel semicanals by a thin, bony septum; the
inferior semicanal represents the auditory tube, which connects the
tympanic cavity to the nasopharynx, and the superior semicanal
houses the tensor tympani muscle

Front 6

TYMPANIC CAVITY

ANTERIOR WALL
-"cochleariform process"

Back 6

B. Tympanic cavity

4. Anterior wall

c. The cochleariform process is formed by the pulleylike posterior end
of the thin, bony septum separating the semicanals; over this process, the tendon of the tensor tympani bends laterally at a right angle
to reach its insertion on the superior part of the manubrium of the
malleus