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Front 1

ANTERIOR SEMICIRCULAR CANAL

Back 1

3. Anterior semicircular canal

a. Positioned upright and perpendicular to the petrous ridge; it pro-
duces the arcuate eminence in the middle cranial fossa

b. Its lateral crus opens into the lateral region of the vestibule and ex-
hibits an ampulla; its medial crus joins the anterior crus of the pos-
terior semicircular canal to form the common crus

Front 2

POSTERIOR SEMICIRCULAR CANAL

Back 2

4. Posterior semicircular canal: positioned upright and parallel to the pe-
trous ridge; its anterior crus forms the common crus with the medial crus
of the anterior semicircular canal and its ampullary posterior crus opens
into the posterior region of the vestibule

Front 3

LATERAL SEMICIRCULAR CANAL

Back 3

5. Lateral semicircular canal

a. Positioned horizontally when the chin is tilted downward 30 degrees

b. Its anterior ampullary crus opens into the vestibule inferior to the
ampulla of the anterior semicircular canal and produces the promi-
nence of the lateral semicircular canal on the medial wall of the tym-
panic cavity; its posterior crus opens into the posterior region of the
vestibule near the ampullary posterior crus of the posterior semicir-
cular canal

Front 4

CC

FUNCTIONAL INTEGRITY OF SEMICIRCULAR DUCTS

Back 4

6. Clinical note: the functional integrity of the semicircular ducts may be
tested by revolving an individual; this will cause flow of endolymph in
the semicircular ducts that will stimulate their sensory hair cells and
produce a nystagmus or oscillation of the eyes

Front 5

CC

COCHLEA: DESCRIBE

Back 5

E. Cochlea

1. The cochlea resembles a snail shell that makes two and three-quarter
turns from its base to its apex or cupula; the basal turn produces the
promontory and the apex points anterolaterally

Front 6

CC

COCHLEA: CONSISTS OF...

Back 6

E. Cochlea

2. The cochlea consists primarily of two helically arranged chambers of the
bony labyrinth, the scala vestibuli and scala tympani, which are continu-
ous with one another at the apex through an opening called the helico-
trema; the scala vestibuli is continuous proximally with the vestibule and
the scala tympani ends distally at the secondary tympanic membrane
within the round window

Front 7

COCHLEA

COCHLEAR DUCT
-arrangment
-contains

Back 7

3. The cochlear duct is also helically arranged and interposed between the scala vestibuli and scala tympani; it contains the sensory hair cells of the
organ ofCorti, the organ of hearing, and communicates with the sac-
cule through the ductus reunions