HUMAN BIOLOGY

cervix Lower part of the
uterus.

endometrium The uterus
lining.

estrogens Female sex
hormones that influence
the development of female
secondary sexual traits and
function in the menstrual
cycle.

gametes Eggs and sperm.

germ cells Cells that give
rise to gametes.

menstrual cycle Monthly
cycle in a sexually mature
female during which an
oocyte matures and is
released from an ovary.

oocytes Immature eggs.

ovaries The primary repro-
ductive organs of females.

oviduct Tube that carries
oocytes (eggs) from an
ovary to the uterus.

secondary sexual
trait Trait that is associated
with maleness or female-
ness, but that is not directly
involved with reproduction.

uterus Organ in which a
baby can grow and develop
prior to birth.

vagina Channel that
receives the penis and
sperm and serves as part
of the birth canal.

the Female reproductive system

n    The biological function of the female reproductive system

is to nurture developing offspring from the time of

conception until birth.

Remember from Section 15.11 that ovaries are a female’s

primary reproductive organs—her gonads. The ovaries

contain germ cells that produce eggs. The word germ

comes from a Latin word that means

“to sprout.” A male also has germ

cells, in his testes. Eggs and sperm

are sometimes called gametes

(gam-eets), from a Greek word that

means “to marry.” Reproductive

organs in both sexes also release

hormones that guide reproduction

and the development of secondary

sexual traits.

Ovaries are a female’s primary reproductive organs

Figure 16.1 shows the parts of the

female reproductive system and

summarizes their functions. The

ovaries release sex hormones includ-

ing estrogens, and during a woman’s

reproductive years they also pro-

duce eggs. Estrogens influence the

development of female secondary

sexual traits, such as the “filling out”

of breasts, hips, and buttocks by fat

deposits. Estrogens also help gov-

ern the menstrual cycle, described

shortly.

Immature eggs are called

oocytes. When an oocyte is released

from an ovary, it moves into a nearby

oviduct (also called a fallopian tube).

Fertilization usually occurs while an

egg is in an oviduct. Regardless, an

egg travels down the oviduct into

the uterus. In this organ, a baby can grow and develop.

The wall of the uterus consists of a thick layer of smooth

muscle (the myometrium) and a lining, the endometrium.

The endometrium includes epi thelium, connective tissue,

glands, and blood vessels. The lower part of the uterus is

the cervix. The muscular vagina leads from the cervix to

the outside. It receives the penis and sperm and serves as

part of the birth canal.

A female’s outer genitals collectively form the vulva.

Outermost are a pair of fat-padded skin folds, the labia

majora. They enclose smaller folds, the labia minora, that are

laced with blood vessels. The labia minora partly enclose

the clitoris, a small organ sensitive to sexual stimulation.

A female’s urethra opens about midway between her

clitoris and her vaginal opening. Whereas in males the ure-

thra carries both urine and sperm, in females it is separate

and is not involved in reproduction.

during the menstrual cycle, an oocyte

is released from an ovary

Like all female primates, a woman has a menstrual cycle.

It takes about 28 days to complete one cycle, although this

can vary from month to month and from woman to woman.

During the cycle, an oocyte matures and is released from

an ovary. Meanwhile, hormones are preparing the endome-

trium to receive and nourish an embryo in case the oocyte

is fertilized. If the oocyte is not fertilized, a blood-rich fluid

clitoris

urethra

vagina

anus

labia minora

labia majora

A

F i g u r e 16.1 Animated! The female reproductive system

includes ovaries, oviducts, the uterus, the cervix, and the

vagina. A diagrams the female genitals (vulva). B shows where

the internal reproductive structures are located in the pelvic

cavity. C diagrams these and related structures and summarizes

their functions. (© Cengage Learning)

ovary

uterus cervix

oviduct

bladder

vagina

B

16.1

306 Chapter 16

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