CHAPTER 19
Female Reproductive System
371
5.
Postovulatory structures
:
After ovulation, the remainder
of the graaF
an follicle develops into the
corpus luteum
(±ig. 19-7A) and continues to produce steroid hormones. If
fertilization and implantation occur, the corpus luteum will
remain active and continue to produce progesterone during
the F rst 6 months of pregnancy. If fertilization does not
occur, the corpus luteum degenerates after 10 to 14 days and
becomes the
corpus albicans
(±ig. 19-7B).
Oviducts (Fallopian Tubes)
The
oviducts
are paired, muscular, open-ended tubes that receive
the ovum and provide an ideal environment for fertilization. Each
oviduct has four regions: the
infundibulum
,
ampulla
,
isthmus
,
and
intramural portion
(±ig. 19-1). ±ertilization usually occurs in
the ampulla of the oviduct. The oviduct wall has a
mucosa
con-
taining ciliated cells and secretory (peg) cells in its epithelium, a
muscularis layer
, and a
serosa
outer covering (±ig. 19-9A,B).
Uterus
The
uterus
is a pear-shaped muscular organ that
connects
to the two oviducts and to the vagina via the cervix. It is
the site for
implantation
and
placentation
.
Implantation
is the attachment of the
blastocyst
to the uterine wall;
pla-
centation
is the establishment of a
placenta
that nourishes
the developing embryo and fetus via the
umbilical cord
.
The uterus has a thick wall, which consists of
endometrium
(mucosa),
myometrium
(muscularis), and
serosa
. The uterus
can be divided into three regions: the
fundus
,
body
, and
cervix
(±ig. 19-1). The endometrium undergoes the following mor-
phological and functional changes during the menstrual cycle.
1.
Menstrual phase
:
This is the initial stage (from days 1 to 4
of the cycle). The functional layer (
functionalis
) of the
endometrium sloughs off and bleeds about 2 weeks after
ovulation if fertilization does not occur (±ig. 19-10A).
2.
Proliferative phase
:
±ollowing the menstrual phase (days
5–14 of the cycle), the functionalis of the endometrium
recovers and rebuilds itself. Its glands appear straight, and
its surface is smooth (±ig. 19-10B).
3.
Secretory phase
:
At this phase (days 15–28 of the cycle), the
endometrium becomes ready for implantation. The endo-
metrium thickens, and the glands appear coiled with large
lumens and a sawtooth appearance. These changes are mainly
infl uenced by
progesterone
(±ig. 19-10C). If a
blastocyst
becomes
embedded in the endometrium (
implantation
), the development
of the placenta takes place within a short time (±ig. 19-11A).
Vagina
The
vagina
is a muscular tube that connects the cervix to the
external genitalia. It consists of
mucosa, muscularis
, and
adven-
titia
(±ig. 19-14B) and functions as a copulatory organ and
birth passage.
Mammary Glands
The
mammary glands
are paired exocrine glands located
beneath the skin on the chest. These glands can be classiF ed as
compound tubuloalveolar glands
. In the female, the mammary
glands undergo morphological and functional changes in response
to female hormones (
estrogen, progesterone
). In later pregnancy,
the mammary glands prepare to produce milk (
lactation
) for the
newborn infant (±igs. 19-15A–C and 19-16A).
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