Reproductive System

1. The Male Reproductive System
Dr. Ngabirano Derek

2. Male Reproductive system organs
● Include the testes (male gonads), a system of ducts (including the epididymis,
ductus deferens, ejaculatory ducts, and urethra), accessory sex glands (seminal
vesicles, prostate, and bulbourethral glands), and several supporting structures,
including the scrotum and the penis.
● The testes produce sperm and secrete hormones.
● The duct system transports and stores sperm, assists in their maturation, and
conveys them to the exterior.
● Semen contains sperm plus the secretions provided by the accessory sex glands.
● The penis delivers sperm into the female reproductive tract and the scrotum
supports the testes.

5. Scrotum
● The scrotum is the supporting structure for the testes, consists of loose skin and an underlying
subcutaneous layer that hangs from the root (attached portion) of the penis
● Externally, the scrotum looks like a single pouch of skin separated into lateral portions by a median
ridge called the raphe.
● Internally, the scrotal septum divides the scrotum into two compartments, each containing a single
testis.
● The septum is made up of a subcutaneous layer and muscle tissue called the dartos muscle
● Associated with each testis in the scrotum is the cremaster muscle.
● The cremaster muscle consists of a series of small bands of skeletal muscle that descend, as an
extension of the internal oblique muscle, through the spermatic cord to surround the testis.

6. Scrotum cont.
● The location of the scrotum and the contraction of its muscle fibers regulate the temperature of the
testes.
● Normal sperm production requires a temperature about 2–3°C below core body temperature.
● This lowered temperature is maintained within the scrotum because it is outside the pelvic cavity.
● In response to cold temperatures, the cremaster and dartos muscles contract.
● Contraction of the cremaster muscles moves the testes closer to the body, where they can absorb
body heat.
● Contraction of the dartos muscle causes the scrotum to become tight (wrinkled in appearance), which
reduces heat loss.
● Exposure to warmth reverses these actions.

7. Vasculature of the scrotum
● The blood supply of the scrotum arises from the internal pudendal branch of
the internal iliac arteries, the cremasteric branch of the inferior epigastric
arteries, and the external pudendal arteries from the femoral arteries.
● The scrotal veins follow the arteries.
● The scrotal nerves arise from the pudendal nerves, posterior cutaneous nerves
of the thigh, and ilioinguinal nerves.

9. Testes
● The testes or testicles, are paired oval glands in the scrotum measuring about
5 cm (2 in.) long and 2.5 cm (1 in.) in diameter
● Each testis (singular) weighs 10–15 grams.
● The testes develop near the kidneys, in the posterior portion of the abdomen,
and they usually begin their descent into the scrotum through the inguinal
canals (passageways in the lower anterior abdominal wall during the latter half
of the seventh month of fetal development

10. Testes cont.
● The testes are partially covered by a serous membrane called the tunica
vaginalis which is derived from the peritoneum and forms during the descent
of the testes.
● Like other serous membranes, it has a visceral layer and a parietal layer and
forms a fist-in-balloon relationship with the testis.
● A collection of serous fluid in the cavity of the tunica vaginalis is called a
hydrocele.
● It may be caused by injury to the testes or inflammation of the epididymis.
Usually, no treatment is required.

11. Testes cont.
● Internal to the visceral layer of the tunica vaginalis, the testis is surrounded by
a white fibrous capsule composed of dense irregular connective tissue, the
tunica albuginea;
● it extends inward, forming septa that divide each testis into a series of internal
compartments called lobules.
● Each of the 200–300 lobules contains one to three tightly coiled tubules, the
seminiferous tubules, where sperm are produced.

14. Epididymis
● The epididymis is an organ about 4 cm (1.5 in.) long that curves along the superior
and posterior border of each testis having a comma-shape in profile.
● Each epididymis consists mostly of the tightly coiled ductus epididymis.
● The efferent ducts from the testis join the ductus epididymis at the larger, superior
portion of the epididymis called the head.
● The body is the narrow midportion of the epididymis, and the tail is the smaller,
inferior portion.
● At its distal end, the tail of the epididymis continues as the ductus (vas) deferens
(discussed shortly).

15. Epididymis cont.
● The ductus epididymis would measure about 6 m (20 ft) in length if it were
straightened out.
● It is lined with pseudostratified columnar epithelium and encircled by a layer of
smooth muscle.
● The free surfaces of the columnar cells contain stereocilia, long, branching
microvilli that increase surface area for the reabsorption of degenerated
sperm.
● Connective tissue around the muscle layer attaches the loops of the ductus
epididymis to one another and carries blood vessels and nerves.

16. Epididymis cont.
● Functionally, the epididymis is the site of sperm maturation, the process by
which sperm acquire motility and the ability to fertilize an ovum.
● This occurs over a period of about 14 days.
● The epididymis also stores sperm and during sexual arousal helps propel
sperm into the ductus (vas) deferens by peristaltic contraction of its smooth
muscle.
● Sperm may remain in storage in the epididymis for up to several months.
● Any stored sperm that are not ejaculatted by that time are eventually
phagocytized and reabsorbed.

17. Ductus Deferens
● Within the tail of the epididymis, the ductus epididymis becomes less convoluted,
and its diameter increases.
● Beyond this point, the duct is referred to as the ductus deferens or vas deferens.
● The ductus deferens, which is about 45 cm (18 in.) long, ascends along the
posterior border of the epididymis, through the spermatic cord to the point in the
lower abdominal wall where it passes through the inguinal canal to enter the pelvic
cavity; there it loops over the ureter and passes over the side and down the
posterior surface of the urinary bladder.
● The dilated terminal portion of the ductus deferens is known as the ampulla

18. Ductus Deferens cont.
● The mucosa of the ductus deferens consists of pseudostratified columnar
epithelium and lamina propria (made up of areolar connective tissue).
● The muscularis is composed of three layers; the inner and outer layers are
longitudinal, and the middle layer is circular
● Functionally, the ductus deferens conveys sperm during sexual arousal from the
epididymis toward the urethra by peristaltic contractions of its muscular coat.
● Like the epididymis, the ductus deferens also can store sperm for several months.
● Any stored sperm that are not ejaculated by that time are eventually reabsorbed

19. Ejaculatory duct
● Each ejaculatory is about 2 cm (1 in.) long and is formed by the union of the
duct from the seminal vesicle and the ampulla of the ductus deferens
● The short ejaculatory ducts form just superior to the base (superior portion) of
the prostate and pass inferiorly and anteriorly through the prostate.
● They terminate in the prostatic urethra, where they eject sperm and seminal
vesicle secretions just before the release of semen from the urethra to the
exterior.

20. Urethra
● In males, the urethra is the shared terminal duct of the reproductive and
urinary systems; it serves as a passageway for both semen and urine.
● About 20 cm (8 in.) long, it passes through the prostate, the deep muscles of
the perineum, and the penis, and is subdivided into three parts
● The prostatic urethra is 2–3 cm (1 in.) long and passes through the prostate.

21. Urethra cont.
● As this duct continues inferiorly, it passes through the deep muscles of the
perineum, where it is known as the intermediate (membranous) urethra
● The intermediate urethra is about 1 cm (0.5 in.) in length.
● As this duct passes through the corpus spongiosum of the penis, it is known as
the spongy (penile) urethra, which is about 15–20 cm (6–8 in.) long.
● The spongy urethra ends at the external urethral orifice.

22. Spermatic cord
● The spermatic cord is a supporting structure of the male reproductive system that
ascends out of the scrotum.
● Each spermatic cord consists of a ductus deferens as it ascends through the
scrotum, the testicular artery, both somatic and autonomic nerves, veins that drain
the testis and carry testosterone into the circulation (the pampiniform plexus),
lymphatic vessels, the cremaster muscle and a fascial covering.
● The spermatic cord and ilioinguinal nerve pass through the inguinal canal, an
oblique passageway in the anterior abdominal wall just superior and parallel to the
medial half of the inguinal ligament.

23. Spermatic cord cont.
● The canal, which is about 4–5 cm (about 2 in.) long, originates at the deep
(abdominal ) inguinal ring, a slitlike opening in the aponeurosis of the transversus
abdominis muscle; the canal ends at the superficial (subcutaneous) inguinal ring, a
somewhat triangular opening in the aponeurosis of the external oblique muscle.
● In females, the round ligament of the uterus and ilioinguinal nerve pass through the
inguinal canal.
● The term varicocele refers to a swelling in the scrotum due to varicosities in the
veins that drain the testes.
● It usually disappears when the person lies down, and typically does not require
treatment

24. Accessory Sex Glands
● The ducts of the male reproductive system store and transport sperm cells, but
the accessory sex glands secrete most of the liquid portion of semen.
● The accessory sex glands include the seminal vesicles, the prostate, and the
bulbourethral glands.

25. Seminal vesicles
● The paired seminal vesicles or seminal glands are convoluted pouchlike structures, about 5 cm (2
in.) in length, lying posterior to and at the base of the urinary bladder anterior to the rectum.
● Through the seminal vesicle ducts they secrete an alkaline, viscous fluid that contains fructose
(a mono saccharide sugar), prostaglandins, and clotting proteins unlike those found in blood.
● The alkaline nature of the fluid helps to neutralize the acidic environment of the male urethra and
female reproductive tract that otherwise would inactivate and kill sperm.
● The fructose is used for the production of ATP by sperm.
● Prostaglandins contribute to sperm motility and viability and may also stimulate muscular
contractions within the female reproductive tract.
● The clotting proteins help semen coagulate after ejaculation.

26. Prostate
● The prostate is a single, doughnut-shaped gland about the size of a ping-pong ball.
● It measures about 4 cm (1.6 in.) from side to side, about 3 cm (1.2 in.) from top to bottom,
and about 2 cm (0.8 in.) from front to back.
● It is inferior to the urinary bladder and surrounds the prostatic urethra (Figure 26.9).
● The prostate slowly increases in size from birth to puberty, and then expands rapidly.
● The size attained by age 30 typically remains stable until about age 45, when further
enlargement may occur, constricting the urethra and interfering with urine flow.
● Secretions of the prostate enter the prostatic urethra through many prostatic ducts.
● Prostatic secretions make up about 25 percent of the volume of semen and contribute to
sperm motility and viability.

27. Prostate cont.
● The prostate secretes a milky, slightly acidic fluid (pH about 6.5) that contains
several substances:
○ 1. Citric acid in prostatic fluid is used by sperm for ATP production.
○ 2. Several proteolytic enzymes, such as prostate-specific antigen (PSA),
pepsinogen, lysozyme, amylase, and hyaluronidase, eventually break down the
clotting proteins from the seminal vesicles.
○ 3. The function of the acid phosphatase secreted by the prostate is unknown.
○ 4. Seminalplasmin in prostatic fluid is an antibiotic that can destroy bacteria.
Seminalplasmin may help decrease the number of naturally occurring bacteria in
semen and in the lower female reproductive tract.

28. Bulbourethral Glands
● The paired bulbourethral glands, or Cowper’s glands, each lie inferior to the
prostate on either side of the membranous urethra within the deep muscles of the
perineum; their ducts open into the spongy urethra.
● During sexual arousal, the bulbourethral glands secrete an alkaline substance that
protects the passing sperm by neutralizing acids from urine in the urethra.
● At the same time, they secrete mucus that lubricates the end of the penis and the
lining of the urethra, thereby decreasing the number of sperm damaged during
ejaculation.
● Some males release a drop or two of this mucus upon sexual arousal and erection.
The fluid does not contain sperm cell

31. Penis
● The penis is a supporting structure of the male reproductive system that contains the
urethra
● It is a passageway for the ejaculation of semen and the excretion of urine. It is
cylindrical in shape and consists of a body, glans penis, and a root.
● The body of the penis is composed of three cylindrical masses of tissue, each
surrounded by fibrous tissue called the tunica albuginea
● The two dorsolateral masses of the body of the penis are called the corpora
cavernosa.
● The smaller midventral mass, the corpus spongiosum penis, contains the spongy
urethra and keeps it open during ejaculation.

32. Penis cont.
● Skin and a subcutaneous layer enclose all three masses, which consist of erectile tissue.
● Erectile tissue is composed of numerous blood sinuses (vascular spaces) lined by
endothelial cells and surrounded by smooth muscle and elastic connective tissue
● The distal end of the corpus spongiosum penis is a slightly enlarged, acorn-shaped region
called the glans penis; its margin is the corona.
● The distal urethra enlarges within the glans penis and forms a terminal slitlike opening,
the external urethral orifice.
● Covering the glans in an uncircumcised penis is the loosely fitting prepuce or foreskin.

33. Penis cont.
● The root of the penis is the attached portion (proximal portion).
● It consists of the bulb of the penis, the expanded posterior continuation of
the base of the corpus spongiosum penis, and the crura of the, the two
separated and tapered continuations of the corpora cavernosa penis.
● The bulb of the penis is attached to the inferior surface of the deep muscles
of the perineum and is enclosed by the bulbospongiosus muscle.
● Contraction of the bulbospongiosus muscle aids ejaculation.

34. Penis cont.
● Each crus of the penis bends laterally away from the bulb of the penis to attach to
the ischial and inferior pubic rami and is surrounded by the ischiocavernosus
muscle
● The weight of the penis is supported by two ligaments that are continuous with the
fascia of the penis:
● (1) The fundiform ligament arises from the inferior part of the linea alba;
● (2) the suspensory ligament of the penis arises from the pubic symphysis.

37. END
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