Unique for its role in human reproduction, a gamete is a specialized sex cell carrying 23 chromosomes—one half the number in body cells. At fertilization, the chromosomes in one male gamete, called a sperm (or spermatozoon), combine with the chromosomes in one female gamete, called an oocyte. The function of the male reproductive system is to produce sperm and transfer them to the female reproductive tract. The paired testes are a crucial component in this process, as they produce both sperm and androgens, the hormones that support male reproductive physiology. In humans, the most important male androgen is testosterone. Several accessory organs and ducts aid the process of sperm maturation and transport the sperm and other seminal components to the penis, which delivers sperm to the female reproductive tract. Scrotum The testes are located in a skin-covered, highly pigmented, muscular sack called the scrotum that extends from the body behind the penis. This location is important in sperm production, which occurs within the testes, and proceeds more efficiently when the testes are kept 2 to 4°C below core body temperature. The dartos muscle makes up the subcutaneous muscle layer of the scrotum. It continues internally to make up the scrotal septum, a wall that divides the scrotum into two compartments, each housing one testis. Descending from the internal oblique muscle of the abdominal wall are the two cremaster muscles, which cover each testis like a muscular net. By contracting simultaneously, the dartos and cremaster muscles can elevate the testes in cold weather (or water), moving the testes closer to the body and decreasing the surface area of the scrotum to retain heat. Alternatively, as the environmental temperature increases, the scrotum relaxes, moving the testes farther from the body core and increasing scrotal surface area, which promotes heat loss. Externally, the scrotum has a raised medial thickening on the surface called the raphae. Testes The testes (singular = testis) are the male gonads—that is, the male reproductive organs. They produce both sperm and androgens, such as testosterone, and are active throughout the reproductive lifespan of the male. Paired ovals, the testes are each approximately 4 to 5 cm in length and are housed within the scrotum. They are surrounded by two distinct layers of protective connective tissue. The outer tunica vaginalis is a serous membrane that has both a parietal and a thin visceral layer. Beneath the tunica vaginalis is the tunica albuginea, a tough, white, dense connective tissue layer covering the testis itself. Not only does the tunica albuginea cover the outside of the testis, it also invaginates to form septa that divide the testis into 300 to 400 structures called lobules. Within the lobules, sperm develop in structures called seminiferous tubules. During the seventh month of the developmental period of a male fetus, each testis moves through the abdominal musculature to descend into the

2. ANATOMY AND
PHYSIOLOGY OF
MALE
REPRODUCTIVE
SYSTEM
This Photo by Unknown Author is licensed under CC BY-SA

4. • INTERNAL STRUCTURES
• Epididymis
 This is a tightly coiled tube that is responsible for
conducting the sperm from the tubule to the vas deferens.
 It has a length of approximately 20 feet long.
 Some sperm are stored in the epididymis, along with the
semen.
 The sperm takes an estimated 12 to 20 days of travel along
the epididymis, and a total of 64 days to reach maturity.

6. Vas Deferens
 carry the sperm from the epididymis into the abdominal
cavity where it will end at the ejaculatory duct.
 It is a hollow tube that is protected by a thick fibrous
coating and surrounded by arteries and veins.

8. Seminal Vesicles
 These are two convoluted pouches along the lower
portion of the posterior surface of the bladder.
 The seminal vesicles secrete a liquid that is viscous
and alkaline and has high protein, sugar, and
prostaglandin content, which makes the sperm
increasingly motile.

10. Ejaculatory Ducts
 These ducts pass through the
prostate gland to join the
seminal vesicles and the
urethra.

11. Prostate Gland
 chestnut-sized gland
 situated below the bladder.
 It secretes a thin, alkaline fluid that adds protection to
the sperm from being immobilized by the low pH level
of the urethra.
 The urethra passes through its center like a doughnut.

13. Bulbourethral Glands
 Also called as Cowper’s gland
 located at either side of the prostate gland and
seminal vesicles and empty through the short ducts
towards the urethra.
 Semen is a product of 60% from the prostate gland,
30% from the seminal vesicles, 5% from the
epididymis, and 5% from the bulbourethral glands.

15. Urethra
 It has a length of approximately 8 inches or 18 to 20 cm.

16. External Structures
Scrotum
 support the testes and it regulates
the temperature of the sperm (2-
3°C lower than body temp).
 promote the production and
viability of the sperm
 the scrotum contracts towards the
body during a very cold weather
and relaxes away from the body
during a hot weather.

17. Testes
 2 to 3 cm in width and are encapsulated in a protective, white
fibrous capsule.
 Several lobules are contained in each testis, which also contains
Leydig’s cells that produce testosterone and seminiferous tubules
that produce spermatozoa.
 In most men, one testis is slightly lower than the other to prevent
trauma and easily sit or do any muscular activity.

18. This sagittal view shows the seminiferous tubules, the site of sperm production. Formed sperm are transferred to the
epididymis, where they mature. They leave the epididymis during an ejaculation via the ductus deferens.

19. Penis
 The penis has three parts: two are called the corpus
cavernosa, and the other is the corpus spongiosum.
 These erectile tissues also contain the urethra,
making the penis an outlet for both urinary and
reproductive functions.
 The glans, a sensitive, bulging ridge of tissue, is
located at the distal part of the penis.
 The prepuce, which is a retractable casing of skin,
protects the glans at birth. It is also the part that is
surgically removed during circumcision.

20. Spermatogenesis
Production of sperm
• occurs in the seminiferous tubules that form the bulk of each testis.
The process begins at puberty, after which time sperm are
produced constantly throughout a man’s life.
• Sperm counts—slowly decline after age 35, and some studies
suggest that smoking can lower sperm counts irrespective of age.

22. Structure of Formed Sperm
• Sperm are smaller than most cells in the body;
• the volume of a sperm cell is 85,000 times less
than that of the female gamete.
• Approximately 100 to 300 million sperm are
produced each day.

23. Figure . Sperm cells are divided into a head, containing DNA; a mid-piece, containing mitochondria; and a tail,
providing motility. The acrosome is oval and somewhat flattened.

24. Duct System
• During ejaculation, sperm exit the tail of the
epididymis and are pushed by smooth
muscle contraction to the ductus
deferens (also called the vas deferens).
• The ductus deferens is a thick, muscular
tube that is bundled together inside the
scrotum called the spermatic cord.

25. • From each epididymis, each ductus deferens
extends superiorly into the abdominal cavity
through the inguinal canal in the abdominal
wall.
• Sperm make up only 5 percent of the final
volume of semen,that the male ejaculates.
• The bulk of semen is produced by three
critical accessory glands of the male
reproductive system:
• the seminal vesicles,
• the prostate,
• the bulbourethral glands.

26. Seminal Vesicles
 The paired seminal vesicles are glands that contribute
approximately 60 percent of the semen volume.
 Seminal vesicle fluid contains large amounts of fructose,
which is used by the sperm mitochondria to generate ATP
to allow movement through the female reproductive tract.

27. • Prostate Gland
• It excretes an alkaline, milky fluid to
the passing seminal fluid—now called
semen—that is critical to first
coagulate and then decoagulate the
semen following ejaculation.

28. Testosterone
Testosterone, an androgen, is a steroid
hormone produced by Leydig cells.
The continued presence of testosterone
is necessary to keep the male
reproductive system working properly,
and Leydig cells produce approximately
6 to 7 mg of testosterone per day.
low levels of testosterone can lead to
infertility.

29. AGING AND THE MALE
REPRODUCTIVE SYSTEM
Declines in Leydig cell activity can occur
in men beginning at 40 to 50 years of
age. The resulting reduction in
circulating testosterone concentrations
can lead to symptoms of andropause,
also known as male menopause.
A reduction in spermatogenesis resulting
in lowered fertility is also reported, and
sexual dysfunction can also be associated
with andropausal symptoms.

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