HUMAN REPRODUCTION
Human beings are unisexual with two separate sexes – male and female.
MALE REPRODUCTIVE SYSTEM
What makes up the male
reproductive organs?
• Primary sex organs – the
testes
• Ducts – epididymis, sperm
duct (vas deferens)
• Accessory glands – eg:
prostate gland
• External genitalia – the penis
Scrotum:
The scrotum contains the testes.
Functions:
• Acts as a temperature regulator, keeping the testes 2 to 3◦C lower than body temperature.
▪ The lower temperature is needed for the formation of fertile sperm.
▪ In cold conditions, testes are pulled closer to the abdomen for warmth. In warm conditions, the
testes are suspended well away from the body. In this way, the developing sperm are always kept
at a constant temperature.
• Houses and protects the testes.
Testes:
The testes, two oval structures, are suspended outside the body in the scrotum.
In the embryonic stage, the testes are in the abdominal cavity just below the kidneys. Before birth, they
descend into the scrotum.
• The testes consist of many compartments or lobules, which contain highly convoluted tubules, the
seminiferous tubules. These total about 250 meters in each testis.
• Germinal epithelium lines the tubules.
• Between the tubules are groups of endocrine cells, the interstitial cells, or cells of Leydig.
Functions:
The testes produce:
• Sperm (male gametes), by the germinal layer.
• Testosterone (a male hormone), by the interstitial cells.
,Ducts:
The ducts include the:
• Epididymis
• Sperm duct (vas deferens)
• Urethra
Epididymis:
The seminiferous tubules join to form the epididymis, a highly convoluted tubule about 5 meters long.
Functions:
Immature sperm enter the epididymis where they:
• Mature, to become motile and fertile.
• Are stored for several months.
If they stay there any longer, they are broken down by the epithelial cells of the epididymis and re-
absorbed into the body.
Sperm duct (vas deferens):
The muscular sperm duct is a continuation of the epididymis. It leaves the scrotum, passes through the
prostate gland, and then enters the urethra.
Function:
The sperm duct pushes mature sperm forward by strong peristaltic waves, from the epididymis into the
urethra. This is known as ejaculation.
peristaltic wave = strong contraction of smooth muscle in the walls of ducts.
Urethra:
The urethra is the duct at the end of the uro-genital system leading to the exterior.
Function:
The urethra forms a common duct for the transportation of semen and urine, although these two processes
never occur together.
, Prostate gland:
The prostate gland, a plum-sized gland, surrounds the urethra at the base of the bladder.
With increasing age, this gland may enlarge and exert pressure on the urethra, which slows down the emptying
of the bladder. The prostate gland can be removed surgically.
Function:
The prostate secretes a fluid that aids the transport of the sperm and contains and enzyme that make sperm
more active. This fluid makes up about 1/3 of the seminal fluid (semen).
Cowper’s gland:
The two Cowper’s glands are found at the base of the penis.
Function:
Cowper’s glands produce an alkaline mucous-like fluid when sexually aroused. This fluid:
• Neutralizes acidic urine that may still be present in the urethra.
• Lubricates the urethra and external urethral opening to protect sperm from mechanical damage during
ejaculation.
Penis:
The urethra passes down the male external organ, the penis.
• The penis consists of special spongy tissue (erectile tissue). Running the length there are three sections of
erectile tissue.
▪ Two are situated on the dorsal side: the corpus cavernosa.
▪ One is situated on the ventral side: the corpus spongiosum.
Corpus cavernosa
Dorsal blood vessels
Nerv
e Skin
Central artery
Urethra Corpus
spongiosum
Diagram of cross section through penis
The head of the penis is very sensitive
• The primary mechanism that brings about ejaculation is the dilation of the
and is protected by the foreskin. The
dorsal and central arteries supplying blood to the penis.
foreskin is sometimes removed in a
▪ This allows more blood to fill the three spongy erectile tissue
simple operation known as
chambers, causing the penis to lengthen and stiffen. This is called
circumcision, which may be done for
an erection.
religious or cultural reasons, or simply
▪ Without an erection sperm cannot be transferred to the female’s
because the foreskin is too tight.
vagina during sexual intercourse.
Function:
The penis deposits semen with sperm into the female’s vagina during copulation. In this way, sperm are
brought closer to the egg for fertilization, which increases the chance of fertilization.
Human beings are unisexual with two separate sexes – male and female.
MALE REPRODUCTIVE SYSTEM
What makes up the male
reproductive organs?
• Primary sex organs – the
testes
• Ducts – epididymis, sperm
duct (vas deferens)
• Accessory glands – eg:
prostate gland
• External genitalia – the penis
Scrotum:
The scrotum contains the testes.
Functions:
• Acts as a temperature regulator, keeping the testes 2 to 3◦C lower than body temperature.
▪ The lower temperature is needed for the formation of fertile sperm.
▪ In cold conditions, testes are pulled closer to the abdomen for warmth. In warm conditions, the
testes are suspended well away from the body. In this way, the developing sperm are always kept
at a constant temperature.
• Houses and protects the testes.
Testes:
The testes, two oval structures, are suspended outside the body in the scrotum.
In the embryonic stage, the testes are in the abdominal cavity just below the kidneys. Before birth, they
descend into the scrotum.
• The testes consist of many compartments or lobules, which contain highly convoluted tubules, the
seminiferous tubules. These total about 250 meters in each testis.
• Germinal epithelium lines the tubules.
• Between the tubules are groups of endocrine cells, the interstitial cells, or cells of Leydig.
Functions:
The testes produce:
• Sperm (male gametes), by the germinal layer.
• Testosterone (a male hormone), by the interstitial cells.
,Ducts:
The ducts include the:
• Epididymis
• Sperm duct (vas deferens)
• Urethra
Epididymis:
The seminiferous tubules join to form the epididymis, a highly convoluted tubule about 5 meters long.
Functions:
Immature sperm enter the epididymis where they:
• Mature, to become motile and fertile.
• Are stored for several months.
If they stay there any longer, they are broken down by the epithelial cells of the epididymis and re-
absorbed into the body.
Sperm duct (vas deferens):
The muscular sperm duct is a continuation of the epididymis. It leaves the scrotum, passes through the
prostate gland, and then enters the urethra.
Function:
The sperm duct pushes mature sperm forward by strong peristaltic waves, from the epididymis into the
urethra. This is known as ejaculation.
peristaltic wave = strong contraction of smooth muscle in the walls of ducts.
Urethra:
The urethra is the duct at the end of the uro-genital system leading to the exterior.
Function:
The urethra forms a common duct for the transportation of semen and urine, although these two processes
never occur together.
, Prostate gland:
The prostate gland, a plum-sized gland, surrounds the urethra at the base of the bladder.
With increasing age, this gland may enlarge and exert pressure on the urethra, which slows down the emptying
of the bladder. The prostate gland can be removed surgically.
Function:
The prostate secretes a fluid that aids the transport of the sperm and contains and enzyme that make sperm
more active. This fluid makes up about 1/3 of the seminal fluid (semen).
Cowper’s gland:
The two Cowper’s glands are found at the base of the penis.
Function:
Cowper’s glands produce an alkaline mucous-like fluid when sexually aroused. This fluid:
• Neutralizes acidic urine that may still be present in the urethra.
• Lubricates the urethra and external urethral opening to protect sperm from mechanical damage during
ejaculation.
Penis:
The urethra passes down the male external organ, the penis.
• The penis consists of special spongy tissue (erectile tissue). Running the length there are three sections of
erectile tissue.
▪ Two are situated on the dorsal side: the corpus cavernosa.
▪ One is situated on the ventral side: the corpus spongiosum.
Corpus cavernosa
Dorsal blood vessels
Nerv
e Skin
Central artery
Urethra Corpus
spongiosum
Diagram of cross section through penis
The head of the penis is very sensitive
• The primary mechanism that brings about ejaculation is the dilation of the
and is protected by the foreskin. The
dorsal and central arteries supplying blood to the penis.
foreskin is sometimes removed in a
▪ This allows more blood to fill the three spongy erectile tissue
simple operation known as
chambers, causing the penis to lengthen and stiffen. This is called
circumcision, which may be done for
an erection.
religious or cultural reasons, or simply
▪ Without an erection sperm cannot be transferred to the female’s
because the foreskin is too tight.
vagina during sexual intercourse.
Function:
The penis deposits semen with sperm into the female’s vagina during copulation. In this way, sperm are
brought closer to the egg for fertilization, which increases the chance of fertilization.
