The Reproductive Organs Make, Deliver,
and Receive the Sex Cells
LEARNING OBJECTIVES
1.
Identify
the organs of the male reproductive
system and their functions.
2.
Describe
how sperm are made.
W
e reproduce by
s e x u a l r e p r o d u c t i o n
, a pro-
cess in which sex cells (
g a m e t e s
) unite to
form offspring. The gametes are formed in
the
g o n a d s
. The gametes unite inside the fe-
male in a process called
f e r t i l i z a -
t i o n
. The female then nurtures
the growing embryo until birth. So
the reproductive organs are spe-
cialized for making gametes and
bringing them together for fertil-
ization; in the case of the female,
they also provide a “home” for nurturing the growing em-
bryo.
Let’s start by examining the male reproductive organs.
Male Reproductive Organs
Make and Deliver Sperm
The organs of the male reproductive system are the follow-
ing. (Figure 16.1):
The testes.
A system of ducts:
the
epididymis, vas
deferens,
ejaculatory ducts, and urethra.
Accessory sex glands: seminal vesicles, prostate, and
bulbourethral glands.
Supporting structures: the scrotum and the penis.
The male’s
t e s t e s
(singular:
testis)
make gametes called
s p e r m
. The testes are paired oval glands that lie outside the
body’s core, in a sac called the
s c r o t u m
. They also secrete
the hormone
t e s t o s t e r o n e
, which we will discuss soon.
The scrotum is a pouch that supports the testes. It
consists of loose skin, and smooth muscle. Internally, the
scrotum is divided into two sacs, each containing a single
testis. The scrotum keeps the sperm at an optimal tem-
perature for their development, slightly less than the core
body temperature. Higher temperatures, which may be
caused by tight clothing or certain occupations, may harm
3.
Explain
the functions of hormones in the male
reproductive system.
4.
Identify
the organs of the female reproductive
system and their functions.
the sperm and cause infertility in the male, as we noted in
the chapter opener.
The sperm mature in the tightly coiled ducts of the
e p id id y m is
and are stored in a tube called the
v a s d e f e r -
e n s
(or
ductus deferens).
After they are made and matured, the sperm cells
will
ultimately be
delivered
to
the female via the penis during
s e x u a l in te r c o u r s e
. When a male
becomes
sexually
aroused,
the
spongy tissue of this accessory re-
productive organ (
F ig u r e 1 6 . 1 b
)
becomes engorged with blood un-
til it is stiff and erect; this configuration is necessary for
the penis to be inserted inside the female’s vagina.
During sexual arousal, the sperm get swept (by peri-
staltic contractions) through the vas deferens and ejacu-
latory duct into the urethra, where they are mixed with
secretions from other accessory reproductive organs. The
accessory organs include the following:
P r o s t a t e
. The prostate secretes a milky, slightly acidic
fluid that helps semen coagulate after ejaculation and
subsequently breaks down the clot.
S e m in a l
v e s i c l e s
.
The
seminal
vesicles
secrete
alkaline, viscous fluid that helps neutralize acid in the
female reproductive tract, provides fructose for ATP
production by sperm, contributes to sperm motility and
viability, and helps semen coagulate after ejaculation.
B u lb o u r e t h r a l g la n d
. The bulbourethral (Cowper’s)
glands secrete alkaline fluid that neutralizes the acidic
environment of the urethra, and mucus that lubricates
the lining of the urethra and the tip of the penis during
sexual intercourse.
The mixture of sperm and acces-
sory organ secretions is called
s e -
m e n
. Semen gets expelled from
the body through the urethra of
the penis during
e j a c u la t io n
.
W
g o n a d
(GO-nad) A
gland that produces
gametes and secretes
hormones; the ovaries
in the female and the
testes in the male.
s e x u a l in te r c o u r s e
The insertion of the
erect penis of a male
into the vagina of a
female. Also called
c o itu s
(KO-i-tus).
e ja c u la tio n
(e-jak-
a-LA-shun) The reflex
ejection or expulsion
of semen from the
penis.
470 CHAPTER 16
The Reproductive Systems
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