Chapter 27— The Male
Reproductive System
27-1
Ch. 27 Study Guide
1. Read pp. 1048-1050 of section 27.1 before
prenatal hormones and sexual differentiation
section; also read sections 27.2-27.4
(pp.1053-1067)
2. Comprehend Terminology (those in bold)
3. Study-- Figure questions, Think About It
questions, and Before You Go On (sectionending) questions
4. Do end-of-chapter questions:
– Testing Your Recall— 2-20
– True or False– 1-9
– Testing Your Comprehension– 3, 4
27-2
Said an ovum one night
to a sperm, “You’re a
very attractive young
germ.
Come join me, my sweet,
let our nuclei meet
And in nine months we’ll
both come to term.”
--Isaac Asimov
27-3
27.2. Male Reproductive Anatomy—
A. The Spermatic Ducts and the
Accessory Glands
27-4
§ A. Sperm’s journey
1. Testes– sperm-producing organs;
inside the scrotum (skin-covered sac)
2. Routes (spermatic ducts) the sperm
travel: A-Testes  B-Efferent ductules
 C-Epididymis  D-Ductus deferens
 E-Ejaculatory duct  F-Urethra 
Exterior
Fig. 27.11b
27-5
Anterior/posterior view?
2. Prostate gland
Urinary bladder
Ureter
1. Seminal
vesicle
3.
Bulbourethral
gland
E
F
Penis
D
C
B
Glans penis
A
27-6
§ Spermatic Ducts Include-• Efferent ductules
– 12 small ciliated ducts collecting sperm from rete testes
and transporting it to epididymis
• Epididymis (head, body and tail)
– 6 m long coiled duct adhering to posterior of testis
– site of sperm maturation and storage (fertile for 60 days)
• Ductus (vas) deferens (peristalsis during orgasm)
– muscular tube 45 cm long passing up from scrotum
through inguinal canal to posterior surface of bladder
• Ejaculatory duct
– 2 cm duct formed from ductus deferens and seminal
vesicle and passing through prostate to empty into urethra
Fig. 27.9, 27.11
27-7
§ Male Urethra
1. Three Regions: prostatic,
membranous and penile urethra-- totals 20 cm long (Fig. 20.11b)
2. Function
– It serves both urinary and reproductive
roles
– It cannot pass urine and semen
simultaneously
27-8
Ampulla
Seminal vesicle
Ejaculatory duct
Prostate gland
A
Bulbourethral gland
B
Ductus deferens
Efferent ductules
Testis
Epididymis
C
27-9
§ Accessory Glands-A
1. Sperm is supported by semen from
accessory sex glands-– including the seminal vesicles,
prostate gland, and bulbourethral
glands
27-10
§ Accessory Glands-B
• Seminal vesicles (paired)
– posterior to bladder
– Yellowish alkaline secretion empties into ejaculatory
duct; constitute 60% of the semen
– Containing fructose, sugars, ascorbic acid, a
coagulating enzyme, prostaglandins, proseminogelin
• Prostate gland (single)
– below bladder, surrounds urethra and ejaculatory
duct; digital rectal examination
– 2 x 4 x 3 cm; thin, acidic milky secretion; 30% of the
semen
– Plays a role in activating sperm, containing citrate (a
nutrient), serine protease
27-11
§ Accessory Glands-C
• Bulbourethral glands (paired; Cowper’s
glands)
– near bulb of penis
– empty into penile urethra
– neutralize urine
– lubricating fluid secreted during sexual
arousal
27-12
27.2. Male Reproductive
Anatomy—
B. The Scrotum & Testicular
Thermoregulation
27-13
§ Scrotum
1. Perineum–
Fig. 27.6
2. Pouch (scrotum) holding testes
– divided into 2 compartments by ______ which is
external marked by perineal raphe
3. Spermatic cords– paired structures
consisting of layers of CT and muscle enclosing
ductus deferens, blood and lymphatic vessels, and
testicular nerves.
– Location– each spermatic cord begins at the
entrance to the In-________ canal
Fig. 27.7
27-14
Fig. 27.6--The male perineum
27-15
27-16
§ Testicular Thermoregulation
• Sperm cannot be produced at core body
temperature (too warm):
– 1. pampiniform plexus = near testicular
artery, a network of veins– forming countercurrent
heat exchanger that cools arterial blood entering
testis by 1-2 degree Celsius (Fig. 27.8)
• When Cold:
– 2. cremaster muscle = pulls testes close to
body when cold
– 3. dartos muscle-• Contracts and scrotum becomes taut
• wrinkles skin reducing surface area of scrotum
27-17
27-18
27.2. Male Reproductive
Anatomy—
C. Testes
27-19
§ Testes (Fig. 27.10 a-b)-A
Dimension-- Oval organ; 3 cm (anterior to
posterior) x 2.5 cm (wide) x 4 cm (long)
Each testis is surrounded by two tunics: (From
outermost and moving in)
1.Its anterior and lateral surfaces are
covered by tunica vaginalis
2.Tunica albuginea– testis itself has a
white fibrous capsule
27-20
27-21
Review
spermatic
ducts


27-22
§ Testes (Fig. 27.10 a-b)-B
3. Septa divide testes into 250-300 wedgeshaped lobules containing seminiferous
tubules (where sperm are produced)
– each tubule lined with a thick germinal epithelium
(several layers of germ cells) for sperm production
– Tall Sertoli (sustentacular) cells; function?
4. Between the seminiferous tubules are
interstitial (Leydig) cells, the source of
testosterone
Fig. 27.10 and X
27-23
See next slide
for details of
germ and
sustentacular
cells
27-24
Lumen of seminiferous tubule
Stages of
sperm
maturation: 
Spermatozoon
Tight
junctions
--see next
slide
Sertoli
cell
Spermatids
Secondary
spermatocyte
Primary
spermatocyte
Spermatogonium
27-25
§ Blood-testis barrier of testes
• (Structures) Formed by tight junctions
between sustentacular (Sertoli) cells -separating sperm from blood and immune
systems
• (Functions) Prevents proteins and other
large molecules in the blood and intercellular
fluid from getting to the germ cells
27-26
§ Blood circulation to/from the testis
1. Sperm’s transportation inside the testes-Seminiferous tubules drain into rete testis which
is embedded in the capsule on the posterior side
2. Testicular arteries– arise from the abdominal
aorta; low BP of testicular artery results in poor O2
supply
– sperm develop very large __________ helping
them also survive hypoxic environment of female
reproductive tract
3. Pampiniform plexus of veins and then
testicular veins-- the right one drains to
inferior vena cava; the left one drains into the left
renal vein
27-27
27.2. Male Reproductive
Anatomy—
D. The Penis
27-28
§ Penis (Fig. 27.11, 27.12)
• Internal root; visible (external)-- shaft, and glans
– external portion 4 in. long when flaccid
– skin over shaft loosely attached allows expansion
• extends over glans as prepuce (foreskin)
• 3 cylindrical bodies of erectile tissue
– corpus spongiosum (1) along ventral side of penis
• encloses penile urethra
• at distal end, fill the entire glans
– corpora cavernosa (2)
• On each side; separated by a median septum
• Each is ensheathed in a fibrous tunica albuginea
• diverge like arms of a Y
• each arm, called crus, attaches to pubic arch
covered with ischiocavernosus muscle
27-29
27-30
27-31
27.3. Sperm and Semen—
A. Spermatogenesis
27-32
§ Spermatogenesis--A
1. Def. of spermatogenesis– The
production of sperm cells through a
series of mitotic and meiotic cell
divisions
• Location?
• How long does it take?
• Microscopic examination– two important
cell types (see next slide)
27-33
§ Spermatogenesis--B
2. Two important cell types in
seminiferous tubules
A. Germ cells–
• In various stages of sperm development,
such as spermatogonia, primary
spermatocytes, secondary
spermatocytes
B. Sustentacular (Sertoli) cells– these cells
provide crucial support for
spermatogenesis
Figure 27.15
27-34
27-35
§ Spermatogenesis--C
3.Three major stages—
A. Mitotic proliferation—
• Spermatogonia located in the outermost
layer of the seminiferous tubule, outside the
blood-testis barrier (BTB)
• One of the daughter cells (Type A
spermatogonium) remain at the outer edge of
the tubule; importance?
• The other daughter cell (Type B
spermatogonium) starts moving toward
lumen forming 4 identical primary
27-36
spermatocytes (2N)
§ Spermatogenesis--D
B. Meiosis—
• Each primary spermatocyte (2N) must pass
through BTB (tight junction) and ultimately
yield 4 spermatids (1N)
C. Spermiogenesis—
• Spermatids become extremely
specialized and motile spermatozoa
• Sperm travel lightly
Figure x&y, 27.16
27-37
A.
B.
Meiosis
C.
27-38
Spermatogenesis
Stages:
Spermatogonia
Mitosis
Primary
spermatocyte
First meiotic
division
Meiosis Secondary
spermatocyte
Second meiotic
division
Spermiogenesis
Chromosomes:
One daughter cell remains
at the outer edge of the
seminiferous tubule to
maintain the germ cell line
One daughter cell moves
toward the lumen to
produce spermatozoa
46; 2n
(diploid number;
single strands)
46; 2n
(diploid number;
single strands)
46; 2n
(diploid number;
doubled strands)
23; n
(haploid number;
double strands)
Spermatids
23; n
(haploid number;
single strands)
Spermatozoa
23; n
(haploid number;
Single strands)
27-39
Figure 27.16
27-40
27.3. Sperm and Semen—
B. Spermatozoon
27-41
§ The Spermatozoon--A
• Two parts– the head and the tail
1.Head contains three structures:
A. A nucleus– with a haploid set of
chromosomes
B. Acrosome– a lysosome vesicle in a thin cap;
in the apical half of the head
C. Flagellar basal body– is nestled in an
indentation at the basal end of the nucleus
Fig. 27.17
27-42
27-43
§ The Spermatozoon--B
• Two parts– the head and the tail
2.Tail contains three regions:
A. Midpiece– many large mitochondria coil
around the axoneme (center of the sperm)
and they provide the ATP needed for the tail
B. Principal piece– constitutes most of the tail
and provides motility for the spermatozoon
C. Endpiece– axoneme only; the narrowest part
of the sperm
Fig. 27.17
27-44
Figure 27.17b
27-45
27.3. Sperm and Semen—
C. Semen
27-46
§ Semen (2-5 ml)--A
1. Def.– milky white mixture of sperm and
accessory gland secretions expelled during
orgasm
2. Functions–
A. provides a transport medium and nutrients
(fructose mainly and also citrate and sugars)
B. protects and activates the sperm
• overall alkalinity helps neutralize the acid
environment
• prostaglandins– decrease the viscosity of
mucus guarding the entry of the uterus
27-47
§ Semen--B
– The clotting enzyme from the prostate
activates proseminogelin (from the seminal
vesicles) into seminogelin
– Seminogelin sticks to the walls of the vagina,
ensuring the semen doe not drain back
– 20-30 minutes after ejaculation: serine
protease of the prostatic fluid breaks down
seminogelin and liquefies the semen (sperm
now very active)
27-48
§ Semen—C; Low sperm count?
•
•
•
•
2-5 ml semen per ejaculation
200 million sperm per ejaculation
50-130 million sperm per ml
Low sperm count is < 20 million sperm
per ml of semen (less than the minimal
jackpot of the Powerball)
27-49