MALE
REPRODUCTIVE
SYSTEM
Anatomy of the Male
Reproductive System
• The primary sex organs are the testes.
• The accessory organs include a complex set of ducts
and tubules leading from the testes to the penis.
• The penis is the organ of copulation.
Anatomy of the Male
Reproductive System
Figure 28.11
Scrotum
• The scrotum is a skin-covered sac that provides the testes with a
cooler environment than body temperature.
• Sperm develop successfully at approximately 3 Celsius below
normal body temperature.
• The scrotum is homologous to the labia majora in the female.
• A raphe separates the two scrotal sacs.
• The dartos muscle is a layer of smooth muscle that is part of the wall
of the scrotum.
Scrotum
Figure 28.12
Spermatic Cord
The spermatic cord originates at the inguinal canal. It consists of the following:
• Testicular artery—branch of the
abdominal aorta
• Pampiniform plexus—a network of veins
surrounding the testicular artery
• Cremaster muscle and fascia—formed from
muscle fiber extensions of the internal oblique
muscle
• Autonomic nerves— travel with plexus and connect to
the testes
Spermatic Cord
Figure 28.12
Testes
•
The function of the testes is twofold:
1.production of sperm
2.production and secretion of androgens (male sex hormones), the most
common being testosterone
•
•
Each testis is covered anteriorly and laterally by a serous
membrane called the tunica vaginalis
The tunica vaginalis has an outer parietal layer and an inner
visceral layer
Testes
Figure 28.13
Testes
• Located just deep to the visceral layer and in contact with the testis is
a thick, whitish fibrous capsule covering the testis called the tunica
albuginea.
• The tunica albuginea projects into the interior of the testis as the
mediastinum testis through which blood vessels, lymphatic vessels,
and some nerves enter and leave the testis.
Testes
• The tunica albuginea projects internally into the testes to form septa.
• The septa subdivide to form about 250 lobules.
• Each lobule contains four convoluted seminiferous tubules.
Seminiferous Tubules
Seminiferous tubules contain two types of cells:
1. Sustentacular cells—nondividing support cells that assist with
sperm development; connected to each other by tight junctions
and form the blood-testis barrier
2. A population of dividing germ cells that continuously produce
sperm beginning at puberty
Interstitial Space
• Spaces external to and in between seminiferous tubules
• Interstitial cells reside in these space and produce hormones called
androgens
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Interstitial cells
Seminiferous
tubule
Tubule lumen
Sustentacular
cells
Sperm cells
Spermatids
Spermatogonia
Figure 28.13
LM 250x
(b) Seminiferous tubule, cross section
b: © The McGraw-Hill Companies, Inc./Photo by Dr. Alvin Telser
Spermatogenesis and Spermiogenesis
Figure 28.14
Spermatogenesis and Spermiogenesis
Figure 28.14
Stages of Spermatogenesis
Ducts in the Male Reproductive System
Beginning at the testis and extending through the penis, the ducts are:
• Rete testis
• Efferent ductules
• Epididymis
• Ductus deferens
• Ejaculatory duct
• Urethra
Ducts in the Male Reproductive System
Figure 28.15
Rete Testis
• Receive sperm from seminiferous tubules
Figure 28.13
Efferent Ductules
• Connect rete testis to epididymis
Figure 28.13
Epididymis
•
•
•
Situated on the posterosuperior surface of the testes, the
epididymis has three regions:
- head
- body
- tail
Internally, the epididymis contains a long convoluted duct of the
epididymis
The epididymis stores sperm and serves in the maturation process
of sperm
Epididymis
Figure 28.13
Ductus Deferens
• Sperm leaving the epididymis enter the ductus deferens (vas
deferens).
• This tube travels within the spermatic cord and enters the pelvic
cavity through the inguinal canal.
• As the ductus deferens approaches the prostate gland, it enlarges to
form the ampulla.
• The ampulla unites with the proximal portion of the seminal vesicle to
form the ejaculatory duct.
Ductus Deferens
Figure 28.15
Ejaculatory Duct
• Formed by a uniting of the ductus deferens and the seminal vesicle
• Located within the substance of the prostate gland between 1–2 cm
long and conducts sperm from the ductus deferens to the prostatic
urethra
Ejaculatory Duct
Figure 28.15
Urethra
•
•
Transports semen from both ejaculatory ducts to the outside of the
body
The male urethra is subdivided into three regions:
1. prostatic urethra
2. membranous urethra
3. spongy urethra
Urethra
Figure 28.15
Accessory Glands
•
•
•
There are three glands that secrete fluids to mix with sperm to
create seminal fluid.
These secretions nourish the sperm and neutralize the acidity of
the vagina.
The three glands are as follows:
1.
2.
3.
seminal vesicles
prostate gland
bulbourethral glands
Seminal Vesicles
• The paired seminal vesicles are located on the posterior surface of
the urinary bladder lateral to the ampulla of the ductus deferens.
• They secrete a viscous, whitish-yellow, alkaline fluid containing
fructose and prostaglandins.
Seminal Vesicles
Figure 28.15
Seminal Vesicles
and Prostate Gland
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Seminal vesicle
Prostate
gland
Mucosal folds
in seminal
vesicle
Tubuloalveolar
glands in
prostate gland
LM 25x
(a) Seminal vesicle
LM 80x
(b) Prostate gland
a: © Carolina Biological/Visuals Unlimited; b: © The McGraw-Hill Companies, Inc./Photo by Dr. Alvin Telser
Figure 28.16
Prostate Gland
• The prostate gland is located immediately inferior to the urinary
bladder.
• It produces substances that are secreted directly into the prostatic
urethra.
• Prostatic secretion is slightly acidic and contains mucin, citric acid
(nutrient for sperm), seminalplasmin (antibacterial),and prostaticspecific antigen (PSA, an enzyme that helps liquify semen).
Prostate Gland
Figure 28.15
Prostate Gland
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Ureters
Urinary bladder
Pubic symphysis
Ampulla of ductus deferens
Ductus deferens
Seminal vesicle
Ejaculatory duct
Urogenital diaphragm
Prostate gland
Bulbourethral gland
Urethra
Anus
Penis
Epididymis
Glans
Testis
Scrotum
Figure 28.11
Bulbourethral Glands
• The bulbourethral glands are located in the urogenital diaphragm on
either side of the membranous urethra.
• Mucin is secreted from these glands and enters the spongy urethra at
the base of the penis.
Bulbourethral Glands
Figure 28.15
Semen
• Seminal fluid from the three accessory glands combines with sperm
from the testes to make up semen.
• When released during intercourse, semen is called ejaculate.
• Semen normally measures about 3–5 ml in volume and contains 200–
500 million sperm.
Penis
• The penis and the scrotum form the external genitalia in males.
• Internally, the attached portion of the penis is the root forming both
the bulb and the crura of the penis.
• The body (shaft) is the elongated portion of the penis.
• The tip of the penis is the glans, which surrounds the external
urethral orifice.
Anatomy of the Penis
Figure 28.17
Penis
The shaft of the penis is comprised of three parallel, cylindrical erectile
bodies:
1. Paired corpora cavernosa are located
dorsolaterally and terminate at the distal shaft
of the penis
2. A single corpus spongiosum is inferior and
midline and surrounds the spongy urethra
3. The distal end of the corpus spongiosum
continues within the glans
Anatomy of the Penis
Figure 28.17
Circumcision
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Prepuce
(a) Circumcised penis
(b) Uncircumcised penis
Erection and Ejaculation
• The erectile bodies are composed of venous spaces, which fill with
blood from a central artery to produce an erection.
• Parasympathetic in nervation is responsible for penile erection.
• Ejaculation is the expelling of semen from the penis, in part, by the
rhythmic contraction of the smooth muscle of the urethra.
• Sympathetic in nervation promotes ejaculation.
Development of the
Reproductive Systems
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Sexually Indifferent Stage
Mesonephros
Mesonephric duct
Genital ridge
Paramesonephric
duct
Kidney
Cloaca
Weeks 5–6
Female
Male
Testes
Ovaries
Efferent ductules
Paramesonephric
duct forming the
uterine tube
Epididymis
Mesonephric
duct
(degenerating)
Paramesonephric
duct (degenerating)
Mesonephric duct
forming the ductus
deferens
Fused paramesonephric
ducts forming the uterus
Urinary bladder
(moved aside)
Urinary bladder
Seminal vesicle
Urogenital sinus
forming the urethra
Urogenital sinus forming
the urethra and inferior vagina
Weeks 10–12
Weeks 10–12
Uterine
tube
Urinary bladder
Ovary
Seminal vesicle
Uterus
Prostate gland
Bulbourethral gland
Ductus deferens
Urinary bladder
(moved aside)
Vagina
Figure 28.18
Urethra
Epididymis
Efferent ductules
Testis
Urethra
Hymen
At birth
At birth
Development of the
Reproductive Systems
Figure 28.19