854
UNIT SIX
The uterine wall is thick and composed of three layers
(f
g. 22.29)
. The
endometrium,
the inner mucosal layer, is
covered with columnar epithelium and contains abundant
tubular glands. The
myometrium,
a thick, middle, muscular
layer, consists largely of bundles of smooth muscle F bers in
longitudinal, circular, and spiral patterns and is interlaced
with connective tissues. During the monthly female repro-
ductive cycles and during pregnancy, the endometrium and
myometrium extensively change. The
perimetrium
consists
of an outer serosal layer, which covers the body of the uterus
and part of the cervix.
Vagina
The
vagina
is a F bromuscular tube, about 9 centimeters long,
that extends from the uterus to the outside. It conveys uterine
secretions, receives the erect penis during sexual intercourse,
and provides an open channel for the offspring during birth.
The vagina extends upward and back into the pelvic cav-
ity. It is posterior to the urinary bladder and urethra, anterior
to the rectum, and attached to these structures by connective
tissues. The upper one-fourth of the vagina is separated from
the rectum by a pouch (rectouterine pouch). The tubular
vagina also surrounds the end of the cervix, and the recesses
between the vaginal wall and the cervix are termed
fornices
(sing.,
fornix
). The fornices are clinically important because
they are thin-walled and allow the physician to palpate the
internal abdominal organs during a physical examination.
Also, the posterior fornix, which is somewhat longer than
the others, provides a surgical access to the peritoneal cavity
through the vagina.
The
vaginal orifice
is partially closed by a thin mem-
brane of connective tissue and stratiF
ed squamous epithe-
lium called the
hymen.
A central opening of varying size
allows uterine and vaginal secretions to pass to the outside.
folds and is lined with simple columnar epithelial cells, some
ciliated
(Fig. 22.28)
. The epithelium secretes mucus, and
the cilia beat toward the uterus. These actions help draw
the secondary oocyte and expelled follicular fl
uid into the
infundibulum following ovulation. Ciliary action and peri-
staltic contractions of the tube’s muscular layer aid transport
of the egg down the uterine tube. ±ertilization may occur in
the uterine tube.
Uterus
The
uterus
receives the embryo that develops from an egg
cell fertilized in the uterine tube and sustains its develop-
ment. It is a hollow, muscular organ, shaped somewhat like
an inverted pear.
The
broad ligament,
which also attaches to the ova-
ries and uterine tubes, extends from the lateral walls of the
uterus to the pelvic walls and fl
oor, creating a drape across
the top of the pelvic cavity (see F g. 22.27). A fl attened band
of tissue within the broad ligament, called the
round liga-
ment,
connects the upper end of the uterus to the anterior
pelvic wall (see F
gs. 22.20 and 22.27).
The size of the uterus changes greatly during pregnancy.
In its nonpregnant, adult state, it is about 7 centimeters long,
5 centimeters wide (at its broadest point), and 2.5 centime-
ters in diameter. The uterus is located medially in the ante-
rior part of the pelvic cavity, superior to the vagina, and
usually bends forward over the urinary bladder.
The upper two-thirds, or
body,
of the uterus has a dome-
shaped top, called the
fundus,
and is joined by the uterine
tubes, which enter its wall at its broadest part. The lower one-
third, or neck, of the uterus is called the
cervix.
This tubular
part extends downward into the upper part of the vagina. The
cervix surrounds the opening called the
cervical oriF
ce
(ostium
uteri), through which the uterus opens to the vagina.
FIGURE 22.28
Uterine tube. (
a
) Light micrograph of a uterine tube (800×). (
b
) Falsely colored scanning electron micrograph of ciliated cells that
line the uterine tube (4,000×).
(a)
(b)
Cilia
Cytoplasm
Nucleus
Basement
membrane
Connective
tissue layer
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