Exercise 30
The Male Reproductive System Laboratory Objectives
ferences between the sexes, the adult reproductive systems share
some functional similarities.
On completion of the activities in this exercise, you will be able to:
Describe general characteristics and functions common to
both the male and female reproductive systems.
Describe the overall anatomy and physiology of the male
reproductive system.
Explain the process of spermatogenesis.
Trace the path of sperm cells from their formation through
delivery into the female tract.
Explain the descent of the testes and the clinical relevance
of this process.
• Discuss the roles of the male accessory reproductive
structures.
Describe the composition of semen.
• Discuss the anatomy of the external male genitalia.
• Explain the events that occur during the male sexual
response.
• Both systems produce mature sex cells or gametes: the
spermatozoon (plural = spermatozoa) or sperm cell in
males and the ovum (plural = ova) or egg cell in females.
• Both systems can store, nourish, and transport gametes so
that a sperm cell and an egg cell can fuse together to form a
zygote through a process called fertilization. The forma tion
of the zygote, also called conception, marks the beginning of
a 9-month period of development that produces a new
individual.
• Organs in both systems produce sex hormones and, thus, act
as endocrine glands. These hormones are essential for the
normal development and function of the reproductive
organs .
Both male and female reproductive systems consist of
primary sex organs, or gonads, and accessory sex organs. The
gonads are the testes in the male and the ovaries in the female,
which produce both the gametes and sex hormoncs. The acces­
sory sex organs include various internal glands and ducts as well
as the external genitalia that are found outside the pelviC cav­
ity. These structures nourish, support, and transport the ga­
metes. In addition, the female accessory organs support the
development of the fetus during pregnancy and facilitate the
birth process.
Materials
• Prepared microscope slides
• Testis
• Epididymis
• Vas deferens
• Prostate gland
• Penis
• Sperm smear
• Anatomical model of a sperm cell
Midsagittal section model of the male reproductive
system
he reproductive system is unique to all other organ sys­
tems in the body because it is not necessary for the sur­
vival of the individual , but its activities are absolutely
required for sustaining the human species. Unlike other or­
gans that are functional throughout life. the reproductive or­
gans (also referred to as the genitalia) are inactive until
puberty. At this time. which normally occurs between 11 and
15 years of age. the reproductive organs respond to increased
levels of sex hormones (androgens in males, estrogens in fe­
males) by growing rapidly and becoming functionally mature
structures.
Both the male and female reproductive systems develop from
similar embryonic tissue. In fact. during the first few weeks of
development, male embryos are indistinguishable from female
embryos. As development proceeds, however. two distinct and
special organ systems form. Despite the obvious structural dif­
T
Gross Anatomy of the Male Reproductive System ~.
The testes and accessory sex organs of the male reproductive sys­
tem are illustrated in Figures 30.1 and 30.2. As a system. these
organs function to produce and store sperm cells, to transport
sperm cells along with supporting fluids to the female reproduc­
tive tract during sexual intercourse, and to produce male sex
hormones.
The testes are ovoid structures, about 5 cm long and 3 cm
wide, located within the scrotal sac (scrotum). During fetal de­
velopment, they develop from a retroperitoneal position along
the posterior body wall, close to the kidneys. As the fetus grovvs,
the testes slowly move to a more inferior position in the abdom­
inal cavity. During the seventh month of development, they
make their final descent into the scrotal sac by traveling through
the inguinal canals, passageways that connect the abdominal
cavity with the scrotum. This so-called descent of the testes is
usually complete near the time of birth.
513
EXERCISE THIRTY
Figure 30.1 The male reproductive
system, midsagittal view. Note the
anatomical relations of reproductive struc­
tures with other pelvic organs.
Pubic
symphysis
----,:c:---t-~~­
.......____-..0,
~~)i.I~"-----i~7-11-Seminal
." -+,...-.:......,~'--.;---....;.:.-'---
vesicle
Prostate
gland
Penile urethra _ -,t>.:..:..':"\
Ejaculatory duct
Penis
Ductus deferens
Bulbourethral
gland
Anus
Epididymis
orifice
Scrotum
Ureter
Seminal
vesicle
Glans peniS
Ampulla of vas deferens Corpora cavern os a Ejaculatory - - - --+­
duct Corpus
spongiosum
Prostate gland
Urethra
Vas deferens
Bulbourethral gland
Crura
- - 1 , - - - Epididymis - 1 - - - - Testis
Figure 30.2 The male urogenital system, dissected view_ Note the
pathway of the accessory ducts and the components of the penis.
CLINICAL CORRELATION
In some cases, particularly in premature births, one or both testes
do not complete the migration into the scrotum and remain in
the abdominal cavity or inguinal canals. These so-called
cryptorchid testes will usually descend into the testes within a
few weeks after birth. If normal descent does not occur, the
testes can be surgically moved into the scrotum. If the testes re­
main in the abdominal cavity, the individual will become sterile
0
0
because the internal body temperature is 1 to 3 C too high for
normal sperm development. In addition, males with cryptorchid
testes have a higher risk of developing testicular cancer.
As the testes move into the scrotum, associated structures
such as the vas deferens, blood vessels, nerves, and lymphatiCS
travel with them. These other structures are enclosed by con­
nective tissue and muscle to form the spermatic cords.
Inside the scrotum, each testis is enclosed by the tunica
vaginalis, a continuation of the peritoneum that lines the ab­
domino pelvic cavity. Deep to the tunica vaginalis , a fibrous cap­
sule, the tunica albuginea , covers each testis. The tunica
albuginea gives rise to connective tissue septa (partitions) that
divide the testis into approximately 250 lobules. Each lobule
contains three or four highly coiled seminiferous tubules
(Figure 30.3). Along the posterior aspect of each testis, the sem­
iniferous tubules converge to form a tubular network called the
rete testis. The rete testis transports sperm to about 10 to 12 rel­
atively straight efferent ductules that lead direc tly into the epi­
didymis (Figure 30.4a).
The accessory glands include the seminal vesicles,
prostate gland, and bulbourethral (Cowper's) gland. They
produce substances that provide nourishment and support for
the sperm, particularly while they are traveling through the fe­
male reproductive tract after sexual intercourse.
The accessory ducts include the epididymides (singular =
ep ididymis), vasa deferentia (Singular = vas deferens), and
seminal vesicles. During or just prior to ejaculation , sperm cells
and glandular secretions, which comprise the semen, are re­
leased into the accessory ducts by muscular contractions and
transported to the outside.
The external genitalia include those structures that are
found outside the body cavity. They include the scrotal sac
and the penis. Although the testes, epididymides, and por­
tions of th e vasa deferentia are also external s tructures, they
are not considered to be ex ternal genitalia because they are
derived from embryonic tissue found inside the abdominal
cavity.
THE MALE REPRODUCTIVE SYSTEM
Spermatids
Maturing
spermatocytes
Sustentacular
cells
Secondary
spermatocyte
Primary
spermatocyte
preparing
for meiosis I
compartmen,tt_~ ':;;Ea~
Level of bloodtestis barrier -..........
Connective
tissue capsule
Seminiferous tubules
containing spermatozoa
about to be released
into the lumen
Dividiing
Spermatogonia
spermatocytes
Spermatogonium
Interstitial Fibroblast Basal
cells
compartment
(c)
J
Dividing
spermatocytes
Spermatid
Sustentacular -H'-,!-~~
cell
Capillary -+ J./I"~
---i~L~-L~_' .-~~~~~~
Connective tissue
capsule
Heads of maturing
spermatozoa
Interstitial
cells
(b)
Spermatogonium
Figure 30.3 Microscopic structure of the testes. a) Low-power light micrograph illustrating seminiferous tubules
(LM x 100); b) high-power light micrograph and corresponding illustration showing developing sperm cells and sus­
tentacular cells In the wall of a seminiferous tubule, and interstitial cells outside the tubule (LM x 300); c) close-up
View of the seminiferous tubule shOWing the relationship between developing sperm cells and sustentacular cells.
ACTIVITY 30.1 Examining
the Gross Anatomy
of the Male Reproductive System
]. Obtain a model of a midsagittal section of the male repro­
ductive system (Figure 30.1).
2. Within the scolal sac, identify the ovoid testes . If possible
on your model, observe a sectional view of the testes and
identify the lobules that contain the seminiferous tubules,
where spermatogenesis (sperm cell production) occurs
(Figure 30.4a).
3. Identify the epididymis (Figure 30.1). This single, highly
convoluted, tubular structure begins at the superior mar­
gin of the testes. Observe how the epididymiS descends
along the posterior surface of the testes (Figures 30.1 and
30.2). While in the epididymis, sperm cells marure and
become motile. During ejaculation, sperm are propelled
into the vas deferens by smooth muscular contractions
along the epididymal wall. Sperm can be stored in the epi­
didymis for several months, after which they are taken up
and digested by the epithelial cells lining the lumen.
4. Locate the inferior margin of the testes. At this location ,
the epididymiS gives rise to the vas deferens (ductus defer­
ens). Realize that this long muscular tube transports sperm
to the urethra , which begins within the prostate gland.
5. From its beginning, follow the path of the vas deferens to
the urethra (Figures 30.1 and 30.2). As it passes superiorly
into the abdominal cavity, the vas deferens travels with as­
sociated blood vessels and nerves within the spermatic
EXERCISE THIRTY
Spermatic cord
Flagella of spermatozoa -t-~~~~
in lum.en of epididymis
~~~~~~'-~ijJ~r(
Head of -----------,~h'1I'O­
epididymis Efferent ------:~~~~W;}.~
ductules Rete testis --~~~~~~r
Seminiferous -~,,~~~~~ -~~'t-:
tubule
Tunica - -H--------'
albuginea
,....!H--H+- Body of
epididymis
,
Ductus
deferens
,,
scrotal-----==~l~~~~~~~~'fL:.=~- Tail of cavity
Stereocilia
,
Epithelium
of epididymis
,
,,
epididymis (a)
(b)
Figure 30.4 Microscopic structure of the epididymis. a) Illustration of the epididymis, testes, and the ini­
tial portion of the ductus deferens; b) light micrograph of the epididymis (lM x 400). The epididymis is a highly
convoluted tubule lined by a pseudostratified epithelium with stereocilia projeding into the lumen. A large mass
of maturing sperm cells fills the lumen.
cord. It travels through the inguinal canal to enter the ab­
domen. Next , it passes posteriorly and medially into the
pelvic cavity and travels along the lateral aspect of the uri­
nary bladder. After looping over the ureter, it turns infero­
medially along the posterior surface of the bladder and
unites with the duct of the seminal vesicle to form the
ejaculatory duct.
CLINICAL CORRELATION
The presence of the spermatic cords creates areas of weakness along the abdominal waH where the inguinal canals are located. As a result, loops of the small intestine may protrude into the canal and scrotum, resulting in an inguinal hernia. Inguinal hernias are rare in females because spermatic cords are absent. 6. The ejaculatory duct travels into the prostate gland
where it empties into the urethra (Figure 30.1).
7. The urethra is a relatively long tube that conveys both
urine and sperm to the outside. Identify its three regions
(Figure 30.1), as follows:
• The prostatic urethra begins at the internal urethral
orifice in the bladder wall and passes through the
prostate gland.
• The membranous urethra passes through the muscular
urogenital diaphragm along the anterior floor of the
pelvic cavity.
• The penile urethra (spongy urethra) passes through
the corpus spongiosum in the shaft of the penis. It ends
at the external urethral orifice at the tip of the penis
(Figure 30.1).
8. Identify the three major glands of the male reproductive
system (Figures 30.1 and 30.2) .
• The paired seminal vesicles are convoluted sac like struc­
tures located along the posterior surface of the bladder.
As described earlier, the ducts from these glands unite
with the Vasa deferentia to form rhe ejaculatory ducts.
The secretions of the seminal "esicles include fructose
as a source of energy for sperm, prostaglandins that pro­
mote muscular conrractions of female accessory ducts
and the uterus, and substances that promote sperm
motility and protect sperm cells from the femal e's im­
mune system.
• The prostate gland is a chestnut-shaped structure located
just inferior to rhe urinary bladder. The ejacularory ducts
and the first segment of the urethra (prostatic urethra)
pass through the gland. The prostate produces a milky
secretion "vith an alkaline (basic) pH, which protects
sperm cells from their own acidic waste products and
neutralizes the pH of vaginal secretions. Other sub­
stances produced by the prostate enhance sperm motility.
• The bulbourethral (Cowper's) glands are pea-size struc­
tures located inferior to the prostate gland and within
the urogenital diaphragm (Figure 30.1). Upon sexual
THE MALE REPRODUCTIVE SYSTEM
. u:~al. the glands' mucous secretions are released into
th
r
rule urethra. The mucus neutralizes any urine that
ins in the urethra and lubricates the glans penis in
pr pa ra tion for sexual intercourse.
10. The penis conveys urine to the outside during micturition
(urination ) and sperm into the female reproductive tract
during sexual intercourse. Identify its three regions
(F igures 30.1 and 30.2), as follows:
• The root of the penis is attached to the pelViC bone and
urogenital diaphragm .
CLINICAL CORRELATION
--!!SeS of the prostate gland are common, particularly among
:: _ er age 50. Benign prostatic hyperplasia (BPH) is a
~cancerous tumor that causes enlargement of the prostate and
alon of the urethra . Individuals with this condition can ex­
_ . : 'lee difficulty with micturition (urination), retention of urine
- : e bladder, urinary tract infections, and development of kidney
_": ~~5. Since the prostate is located anterior to the rectum, a digi­
".2 "ectai exam can be done to determine if the prostate is en­
:;rged. Treatment for BPH ranges from drug therapies that reduce
. e tumor to surgical removal of the prostate.
Prostate cancer, a far more serious and potentially deadly
d sease, also causes enlargement of the prostate and constriction
o~ he urethra. This type of cancer is usually without symptoms
duri ng the early stages. If left undetected, secondary tumors
(metastases) can form in nearby lymph nodes, pelvic bones, and
lumbar vertebrae. Early detection is now possible by performing a
blood test for elevated levels of a prostate enzyme known as
prostate-specific antigen (PSA). Treatment for prostate cancer in­
cludes surgical removal of the gland or radiation therapy, in which
small radioactive pellets are placed into the gland and specifically
attack the cancerous tumor. The prognosis is very encouraging if
treatment occurs before a secondary tumor forms. If a metastasis
is detected, treatments are not as effective. However, prostate
cancer grows so slowly that if it occurs after the age of 70, men
usually die of natural causes or other diseases related to aging
rather than the cancer itself. For this reason, sometimes the best
treatment for prostate cancer may be no treatment at all.
WHAT'S IN A WORD Although their name is rather lengthy, the
tiny bulbourethral glands are aptly named. The term describes
their positions-they are located bet',veen the bulb of the penis
and the urethra.
9. Identify the scrotal sac (scrotum), and notice that it is sus­
pe nded inferiorly from the floor of the pelvis , posterior to
the penis , and anterior to the anus. Internally, the scrotum
is divided into two chambers by a connective tissue parti­
tion. Within each chamber are a testis, an epididymis, and
the initial portion of a spermatic cord (Figure 30.1). The
wall of the scrotum consists of skin and superfiCial fascia.
In addition, two layers of muscle are present. In the dermis ,
there is a thin layer of smooth muscle known as the dartos
muscle. Contractions of this muscle create wrinkling in the
skin that covers the scrotum. Deep to the dermis is a
thicker layer of skeletal muscle called the cremaster mus­
cle. If air or body temperature increases, the cremaster
muscle relaxes and the testes are drawn farther from the
body's core. Conversely, a decline in temperature causes the
muscle to contract and brings the testes closer to the body.
• The shaft (body of the penis) is the elongated cylindri­
cal portion.
• The glans penis is the expanded tip of the shaft.
11. Identify the three columns of erectile tissue inside the pe­
nis. They include two dorsal columns known as the
corpora cavernosa, and a single ventral column called
the corpus spongiosum, which transmits the penile ure­
thra ( Figures 30.1 and 30.2). In the shaft , the corpora cav­
emosa form two cylindrical structures that travel parallel
to each other. At the root o f the penis, they diverge to
form the crura of the penis (Figure 30.2 ) and attach to
the pelvis. The corpus spongiosum also has a cylindrical
shape as it passes through the shaft. At the root of the pe­
nis, it enlarges as the bulb of the penis , which attaches to
the urogenital diaphragm. Distally, the corpus spongiosum
expands to form the glans penis, vvhich bears the external
urethral orifice (Figures 30.1 and 30.2).
12. The skin covering the penis is relatively thin and moves
freely over the surface. Identify the fold of skin caJlIed the
prepuce (foreskin) that covers the glans p enis
(Figure 30.1). The inner surface of the prepuce contains
glands that secrete a waxy material called smegma.
CLINICAL CORRELATION
Smegma, secreted from the prepuce, provides a favorable envi­
ronment for bacteria. Consequently, bacterial infections are com­
mon in this area. To reduce the risk of infections, the prepuce can
be surgically removed, a procedure known as circumcision. Re­
moval of the prepuce is commonly performed in newborn babies
in the United States. The procedure is controversial, however, be­
cause opponents believe that it is medically unnecessary and
causes undue pain to the baby.
1. During a vasectomy , incisions are made on
each side of the scrotum and the two vasa defer­
e ntia are cut and tied off within the spermatic cord. A man's
testes will still function normally, but he will be infertile. Ex­
plain why. What other structures could potentially be damaged
during a vasectomy? _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
2. If the prostate gland is surgicaUy removed, the functions of
what other structures could be affected by the procedure?
EXERCISE THIRTY
Microscopic Anatomy of the Male
Reproductive System
In the following activity, you will examine the microscopic
structure of various organs in the male reproductive system. As
you examine these structures, be aware that they possess
unique anatomical features that reflect their characteristic
functions.
Examining the Microscopic
Anatomy of Male
Reproductive Organs
ACTIVITY 30.1 The Testes
1. Obtain a slide of a human or mammalian testis.
2. Scan the slide under low magnification. You are viewing a
cross section of the testis, the primary sex organ in the
male (Figure 30.3).
3. Scan along the edge of the section and observe the fibrous
connective tissue covering called the tunica albuginea.
Connective tissue partitions derived from the tunica al­
buginea divide the testis into lobules.
4. Within each lobule of the testes are three or four seminif­
erous tubules. As you scan the slide under low power, the
lobules can be observed throughout the field of view. Each
tubule is surrounded by connective tissue and contains
several layers of cells surrounding a central lumen. Be­
cause of the plane of section, the lumen may not be evi­
dent in some tubule profiles (Figure 30.3a).
5. Observe a seminiferous tubule under high power
(Figures 30.3b and c). Most of the cells in the walls of the
tubules are developing sperm cells. also kno\vn as sper­
matogenic cells. These cells are referred to by several
names , according to their stage of development. At the
base of the tubules are the spermatogonia. These undif­
ferentiated cells are continuously dividing by mitosis.
(Recall from Exercise 3 that cells formed by mitosis have
the exact genetic composition of the original cell.) Some
spermatogonia will differentiate to become primary sper­
matocytes and begin meiosis, a process of sexual cell di­
vision that forms secondary spermatocytes, spermatids,
and finally, spermatozoa (sperm cells). Cells formed by
meiosis have half the amount of DNA as the original cell;
they are not exact genetic copies.
6. As the sperm cells form (spermatogenesis), they move
from the base to the lumen of the seminiferous tubules.
Observe these various cells on the slide and notice the
change in their appearance as you move from the base of
the tubule wall to the lumen. Realize that the spermatogo­
nia are located along the base and the spermatozoa are in
the lumen (Figures 30.3b and c).
7. In addition to the spermatogenic cells, sustentacular (Sertoli) cells are found in the seminiferous tubules (Figures 30.3b and c), extending from the base to the lu­
men of the tubules and completely surrounding the sper­
matogenic cells. They nourish the spermatogenic cells and
regulate spermatogenesis. On the slides that you are ob­
serving, it is difficult to identify sustentacular cells, but
you should realize that they are present.
8. Scan the slide under high power and observe areas of con­
nective tissue between seminiferous tubules. These inter­
stitial areas contain the interstitial (Leydig) cells
(Figures 30.3b and c) that produce and secrete male sex
hormones, or androgens. The primary hormone produced
is testosterone.
The term androgen is derived from the
Greek words andros, which means "male," and genos, which
means "birth or give rise to. " Androgens are hormones that are
responsible for (give rise to) maleness. Both men and women
make androgens , but these hormones can also be converted into
the female hormones called estrogens.
WHAT'S IN A WORD
The Epididymis
1. Obtain a slide of the epididymiS and scan the slide with the low-power objective lens. 2. Observe the numerous sectional profiles of tubules in the
epididymis (Figure 30.4b). You are actually viewing one
continuous tubule that is highly convoluted.
3. Switch to the high-power objective lens. Notice that the
epithelium lining the lumen is pseudostratified columnar.
Identify the elongated microvilli , known as stereocilia
(despite the name, these structures are not cilia) extending
into the lumen from the surfaces of the epithelial cells
(Figure 30.4b). The stereocilia absorb testicular fluid and
provide nutrients to the sperm cells.
4. In the lumina of some tubule profiles, yo u will see masses
of sperm cells. Observe the sperm masses uncler higher
magnification (Figure 30.4). The sperm that enter the epi­
didymis from the testes are nonmotile. While they move
along the tubule of the epididymis, spermatozoa become
mature and gain the ability to swim.
Vas Deferens
1. Obtain a slide of the vas deferens (ductus deferens) in cross section. 2. Scan the slide with the low-power objective lens and iden­
tify the following tissue layers (Figure 30.5).
• The mucous membrane lines the lumen . It consists of
the epithelium and underlying connective tissue, the
lamina propria.
• The relatively thick smooth muscle layer consists of
three layers. The inner and outer layers are longitudinal
and the middle layer is circular. The muscle layer con­
tracts rhythmically to propel sperm forward during ejac­
ulation.
• The adventitia is a layer of fibrous and loose connective
tissue that covcrs the smooth muscle laycr. It blends in
with the connectivc tissue of adjacent structures.
THE MALE REPRODUCTIVE SYSTEM
Glandular ~:--'---~~--'::..!c..~~
regions
outer--~~~~~~~~~~~~~~
longitudinal
Smooth T~~=-~~-=-_
muscle
mUSCle
layer _ __
Middle
circular
muscle
Iayer
Inner
longitudinal
muscle
layer
lr'Po~liP>· I
Connective ~~~"""r-'-'~~
tissue
---{1~~~~
lamina
propria
Figure 30.6 Microscopic structure of the prostate gland. The glands
in the prostate are irregularly shaped and separated by regions that contain
connective tissue and smooth muscle (lM x 100).
Epithelium ---+.~~~~
3. Identify the three columns of erectile tissue: the paired dorsal corpora cavernosa and the single ventral corpus spongiosum (Figure 30.7). Figure 30.5 Microscopic structure of the vas deferens. The wall of the
vas deferens contains three layers of smooth muscle (lM x 100).
3. Switch to the high-power objective lens and view the ep­
ithelium in the mucous membrane more closely. Similar to
the epididymis, the vas deferens possesses a pseudostrati­
fied columnar epithelium with stereocilia projecting from
the free surface of the cells.
Prostate Gland
1. Obtain a shde of the prostate gland .
2. Scan the slide with the low-power objective lens. Notice
that the prostate contains numerous irregularly shaped
glands, separated by areas of smooth muscle and connec­
tive tissue (Figure 30.6).
3. Vie\v a glandular region with the high-power objective lens. Notice that the epithelium in the glands is simple columnar or pseudostratified columnar. 4. Switch back to the low-power objective lens and try to lo­
cate the prostatic urethra (this structure may be absent on
your slide). Notice that the epithelium lining the urethra
is transitional.
What other structures have a transitional epithelium?
4. Identify the tunica albuginea, a tough fibrous connective
sheath that surrounds the corpora cavernosa and the cor­
pus spongiosum.
5. Notice that the penile urethra passes through the corpus spongiosum (Figure 30.7). 6. Switch to the high-power objective lens and examine the
erectile tissue in a corpus cavernosum more closely Erec­
tile tissue contains a vast network of venous sinusoids and
arteries within a meshwork of connective tissue and
smooth muscle. Upon sexual arousal, parasympathetic
nerves relax the smooth muscle surrounding the erectile
tissue and the arteries supplying the penis. As the arteries
dilate , blood flow to the penis increases, the venous sinu­
soids become engorged with blood, and the penis swells,
elongates, and becomes erect. The erection is mail1lained
because the swollen columns of erectile tissue compress
the veins that would normally drain blood from the penis.
At the height of sexual arousal (orgasm), sympathetic
nerves promote the expulsion of semen to the outside
(ejaculation). Under sympathetic control, smooth muscle
along the accessory ducts and glands contracts to force se­
men into the penile urethra. Then, skeletal muscles at the
base of the penis contract to force semen through the pe­
nile urethra and to the outside. Shortly after ejaculation,
sympathetic nerves cause constriction of the penile arter­
ies and contraction of the smooth muscle surrounding the
erectile tissue columns. As a result , blood flow to the peniS
is reduced, the erectile tissue is gradually drained, and the
penis becomes flaccid.
Sperm
Penis
1. Obtain a slide of the penis, cut in cross section.
2. Scan the slide with the low-power objective lens and
observe the general organization of the penis (Figure 30.7).
1. Obtain a slide of a human (or mammalian) sperm smear.
2. Carefully focus the slide under low magnification. When
the spermatozoa (sperm cells) can be identified, switch to
high magnification.
EXERCISE THIRTY
~~~~~~~~~~;t;~"7
~
cavernosa
Corpora
Tunica
albuginea
Urethra
Figure 30.8
Structure of human sperm cells. A sperm ce ll is the only
human cell to possess a flagellum (the tail portion). Notice the lighter stain ­
ing acrosome covering th e tip of the sperm head.
Corpus
spongiosum
1. Identify similarities and differences in the
microscopic structure of th e epididymis and
Figure 30.7
Microscopic structure of the penis. Eredile tissue in the
penis is found in three columns of ti ssue: the paired dorsal corpora caver­
nosa and one ventral corpus spongiosum, through wh ich the penile urethra
passes (lM x 40).
3. Under high magnification, attempt to identify the three
parts of a spermatozoon: the head , neck (body), and tail
(Figure 30.8).
4. Obtain and observe a model that illustrates the structure
of a ma ture spermatozoon. Ident ify the three parts of a
sperm cell (Figure 30.8).
• The head contains th e nucleus with the male genetic
material (DNA). The acrosome is located at the tip of
the head. I t contains enzymes that allow a sperm cell to
penetrate the egg during fertilizati on. You may not be
able to identify the acrosome on the mic.roscope slides
yo u are viewing.
• The neck, or body, contains mitochondria that produce
the ATP needed for sperm motility.
• The tail is a Ilagellum that propels the sperm forward.
vas deferens.
Similarities:
Differences:
2. In the penis, the tunica albuginea surrounding the corpus
spongiosum is less dense and more elastic compared to the
same structure surrounding the corpora cavernosa . As a result,
the corpus spongiosum is less turgid (swoll en) upon erection
than the corpora cavernosa. What is the functional Significance
of this difference 7 (Hint: Consider the position of the penile
urethra. )
Exercise 30 Review Sheet
Name _______________________________________
LabSectio" ___________________________________
The Male Reproductive System
Date ____________~--------------------------
1. Describe the general functions that can be attributed to the reproductive systems in
both sexes.
2. From a functional perspective, why is it necessary for the testes to descend into the
scrotum?
3. What is an inguinal hernia? Why are inguinal hernias more common in males than in
females?
Questions 4-8: Match the structure in column A with the correct description in column B.
B
A
4. Testes
a. The vas deferens and the duct from the seminal vesicle
merge to form this structure.
5. Vas deferens
b. A portion of the urethra passes through this structure.
6. Epididymis
7. Prostate gland
c. Spermatozoa become mature and motile while in this
structure.
8. Ejaculatory duct
d . The corpus spongiosum is found in this structure.
e. Interstitial (Leydig) cells, found in this structure, produce
testosterone.
f. A portion of this structure is located within the spermatic
cord.
9. What is the clinical significance of prostate-specific antigen (PSA)?
10. The secretions [Tom the male accessory glands have an alkaline (basic) pH. What
would be the consequences i[ the pH of these Ouids became more acidic?
EXE RClSE THlRTY
11. What is the cremaster muscle? Describe how the actions of this muscle protect the
testes.
12. Describe the arrangement of the erectile tissue in the penis. How does the penis be­
come erect? If the blood flow along the penile arteries were reduced, how would this af­
fect a man's ability to have an erection 7
13. Review Figure 30.1 and explain why a digital rectal exam is a good procedure for diag­
nosing an en'larged prostate gland.
Questions 14-24: In the following diagram, identify the structures by labeling with the color
that is indicated.
14. Prostate = green
15. Epididymis = blue
16. Corpus cavernosum = red
17. Ejaculatory duct
=
brown
18. Testes = yellow
19. Seminal vesicle = orange
20. Corpus spongiosum
=
light blue
21. Bulbourethral gland = tan
22. Vas deferens = pink
23. Scrotum
=
black
24. Urinary bladder = purple