Female Reproductive Organs Provide
the Site of Fertilization and Nurture
the Developing Embryo
Because fertilization takes place inside the female’s body,
her reproductive organs are specialized to make gametes,
receive the sperm from the male, serve as the site of fertil-
ization, and house and nurture the developing embryo and
later fetus until birth. The organs of the female reproduc-
tive system include the following.
The ovaries, which are the female gonads.
The uterine (fallopian) tubes, or oviducts.
The uterus.
The vagina.
External
organs,
collectively
called
the
vulva
or
pudendum.
The mammary glands.
Around the time of puberty, the female begins to ex-
hibit female secondary sex characteristics, changes regu-
lated by organs to nonreproductive organs and features. In
females, the secondary sex characteristics include devel-
opment of breasts, growth of pubic and axillary hair, and a
rotation of the pelvis to open the birth canal.
Females make gametes called egg cells, or
oocytes,
in the ovaries (Figure 16.6a) through a process called
oogenesis.
The ovaries are paired organs that produce sec-
ondary oocytes and hormones. As we will see soon, the sec-
ondary oocytes are cells that develop into mature ova, or
eggs, following fertilization. The hormones produced by
the ovaries are progesterone and estrogens (the female
sex hormones), inhibin, and relaxin.
A series of ligaments hold the ovaries in position. The
ovarian ligament anchors the ovaries to the uterus, and
the suspensory ligament attaches them to the pelvic wall.
The broad ligament of the uterus attaches to the ovaries
by a double-layered fold of peritoneum.
Unlike males, females do not produce oocytes continu-
ously; all of her oocytes are formed by the time a baby girl
is born. The oocytes do not mature until after puberty;
then they further develop—usually one at a time—in a
monthly reproductive cycle, which we will discuss later in
the chapter.
The two uterine tubes
(fa llo p ia n tu b es)
extend later-
ally from the uterus toward the ovaries. The open, fun-
nel shaped end of each tube, the infundibulum, lies
close to the ovary but is open to the pelvic cavity. The
ovaries release the mature, or secondary, oocytes into
the uterine tubes where fertilization usually takes place.
Fingerlike projections called fimbriae (FIM-bre-e) catch
the egg released from the ovary and direct it into the
tube. The uterine tubes also transport the secondary oo-
cyte to the uterus.
The uterus serves as part of the pathway for sperm
deposited in the vagina to reach the uterine tubes. It is
also the site of implantation of a fertilized ovum, develop-
ment of a fetus during pregnancy, and labor. During re-
productive cycles when implantation does not occur, the
uterus is the source of menstrual flow. The uterus is situ-
ated between the urinary bladder and the rectum and is
shaped like an inverted pear.
Part of the uterus includes the dome-shaped portion
superior to the uterine tubules called the fundus, the ta-
pering central portion called the body, and the narrow
portion opening into the vagina called the cervix. The in-
terior of the body of the uterus is called the uterine cav-
ity. (Figure 16.6b).
The middle muscular layer of the uterus, the myome-
trium, consists of smooth muscle and forms the bulk of
the uterine wall. During childbirth, coordinated contrac-
tions of uterine muscles help expel the fetus.
The innermost part of the uterine wall, the endome-
trium, is a mucous membrane. It nourishes a growing
fetus or is shed each month during menstruation if fertil-
ization does not occur. The endometrium contains many
endometrial glands whose secretions nourish sperm and
the zygote.
The vagina is a tubular canal that extends from the
exterior of the body to the uterine cervix. It is the recepta-
cle for the penis and semen during sexual intercourse, the
outlet for menstrual flow, and the passageway for child-
birth. The vagina is situated between the urinary bladder
and the rectum.
The mucosa of the vagina contain large stores of gly-
cogen. When glygogen decomposes, it produces organic
acids, which retard microbial growth but are also harm-
ful to sperm. Alkaline components of semen, mostly from
the seminal vesicles, neutralize the acidity of the vagina
and increase the viability of sperm. The muscular lay-
er of the vagina is composed of smooth muscle that can
stretch to receive the penis during intercourse and allow
for childbirth.
A thin fold of mucous membrane called the hymen
may partially cover the vaginal orifice, the vaginal open-
ing. The hymen usually breaks and bleeds during the first
sexual intercourse, but it can also break when participat-
ing in sports or other activities.
476 CHAPTER 16
The Reproductive Systems
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