Human Reproduction.
Human reproduction is essential for survival of the species.
Homeostatic controls such as decreased fertility in times of famine,
reduced or loss of cellular functioning due to the ageing process
and death are all essential for the continuity of the species,
however, they have minimal effect on the maintenance of
homeostatic balance of the human body.
Our basic function is to reproduce, however, the male and female
roles are different. Males and females differentiate physically,
psychologically and sociologically, which demonstrates contrasting
sexual behaviour that is not linked to reproduction.
Reproductive organs are protected by the pelvic girdle.
Reproductive organs are not functional until puberty.
Male Reproduction System.
The male reproductive system is functional throughout life.
The male reproductive role starts and ends with intercourse.
Main Functions:
 Production of sperm (male gamete – reproduction cell).
 Transportation of sperm to female.
 Production of male sex hormone (testosterone). Testosterone
controls the development of secondary sexual characteristics
such as change of body during puberty.
1
Prostate Gland.
The prostate gland is a small gland situated between the bladder
and the rectum. It surrounds the beginning of the urethra. The
prostate gland produces two secretions that are carries in semen.
One helps to keep the lining of the urethra moist. The other is
part of the seminal fluid that helps the semen to travel along the
urethra and into the female.
Testes.
The testes are the male gonads (reproductive glands) that are
contained within a sac of skin and muscle called the scrotum. The
testes produce sperm and testosterone. Sperm are developed and
stored in the testes because they need to be kept at a lower
temperature than the average body temperature (35degrees C).
Epididymis.
The epididymis is a tightly coiled tube, which opens from the top
of each testicle, continues down along the side of the testicle, then
straightens out into the vas deferens. Immature sperm is stored
in the epididymis until it matures and can be transported to the
vas deferens.
Vas deferens.
The vas deferens is a duct with small walls leading from the
epididymis to the urethra. Mature sperm is stored in the vas
deferens until it is transported to the urethra during sexual
activity. The sperm is pushed along by muscular contraction of
the muscular walls (peristalsis).
2
Scrotum.
The scrotum is an external sac that contains the testes, epididymid
and vas deferens. The scrotum hangs under the penis. The
scrotum consists of an outer layer of skin and an inner layer of
muscle. It is divided into two halves by a membrane. Each half
contains a testicle. The scrotum supports, protects and maintains
the correct temperature for the testes. The testes are usually
outside the body to keep them around 35degrees C. If the scrotal
temperature drops the muscles contract to bring it closer to the
body thus raising the temperature of the testes. If the
temperature becomes too high, then the muscles relax, causing
the scrotum to fall away from the body, thus lowering the
temperature of the gonads.
Penis.
The penis is the main external organ of the male. It has three
important parts; erectile tissue bodies, prepuce (foreskin) and the
urethra. The penis has three bodies of spongy erectile tissue all
running lengthways down the side of the urethra thus forming a
tube for the urethra. The tip of the penis is formed from erectile
tissue and is known as the glans penis. The eretile tissue is full of
blood vessels. The prepuce protects the glans penis. The penis
has two important functions:
 Excretory organ: It carries urine from the bladder for excretion.
 Reproductive organ: It becomes erect during sexual activity.
The erection is caused by an increase in the amount of blood
circulating in the spongy tissues. This causes the tissues to
swell and the penis becomes enlarged and rigid therefore able
to penetrate the female vagina and safely deliver semen during
intercourse. While sexual intercourse is taking place the body’s
reflexes prevent urine from entering the urethra.
3
Sperm.
Sperm look like tadpoles under a microscope. Each one consists
of a head, (the sex cell with a nucleus containing the genetic
material), a middle, (containing numerous mitochondria that
provide ATP for movement), and the tail, a flagellum (thread like
structure) that propels the sperm along to its destination. One
sperm is required to fertilise one ovum although there are millions
of sperm in semen. The head of the sperm inserts itself into the
ovum and the rest is broken down and reabsorbed. The fertilised
ovum then grows and develops into a baby.
Female Reproductive System.
The female reproductive system is functional until menopause.
The female reproductive role starts with intercourse and ends in
childbirth.
4
Main functions:
 Production of ova (female gamete - egg).
 Receive sperm from male.
 Produce progesterone and oestrogen (female sex hormones).
 Prepare for pregnancy each month.
 Protect and nurture the embryo (fertilised ova – 8th week) and
developing foetus (9th week – birth).
 Deliver the baby at 40 weeks. (Owtch, ooyah, hellppp meeee!)
Uterus (womb).
The fertilised ovum grows into a baby in the uterus. The top end
opens out into the Fallopian tubes (leading to the ovaries). The
cervix at the lower end opens into the vagina and forms the birth
canal. The uterus is a muscular, hollow organ. It is approximately
the size and shape of an upside down pear in its non-pregnant
state. It expands during pregnancy to accommodate the foetus.
The lining of the uterus consists of layers of tissues that respond
to hormonal secretions. Every month the layers prepare for
pregnancy by thickening up to provide a nourishing bed for the
fertilised ovum. Menstruation occurs otherwise.
Cervix.
The cervix is the narrow neck of the uterus that opens into the
vagina. It is normally the width of a pencil however it dilates
during childbirth to allow the baby to pass through. The cervix
forms the first part of the birth canal. The midwife takes
measurements as the cervix dilates to assess the time of birth.
5
Ovaries.
The ovaries are the female gonads. They are approximately the
size and shape of almonds and are positioned on each side of the
uterus just below the Fallopian tubes. The ovaries secrete
progesterone and oestrogen, which are hormones responsible for
female secondary sexual characteristics. The ovaries also store
ova. When girls are born they already have their ova however
they are in immature and contained in follicles. After puberty one
ovum is released every month. This is called ovulation.
Follicle.
Follicles are small structures on the surface of ovaries. They
contain fluid and an ovum. When an ovum is mature for
fertilisation the follicle splits to release the ovum, which then
travels along the Fallopian tube to the uterus.
Fallopian Tubes.
The Fallopian tubes are funnel shaped and start at the top of the
uterus, going along to the ovaries. The Fallopian tubes provide a
passageway for the ovum from the ovaries to the uterus. Ova
become fertilised in the Fallopian tubes.
Vagina.
The vagina is a muscular passage leading from the cervix to the
vulva. It connects the internal sex organs to those on the outside.
Blood vessels within the vagina become swollen and engorged
with blood during sexual intercourse. The vagina has several
purposes:
 It is a passageway for menstrual blood.
 It forms part of the birth canal during labour.
 It is the site for penetration during sexual intercourse.
6
The Vulva.
The vulva is the collective name for the external organs of the
female reproductive system. They include:
Mons pubis: A pad of protective fat over the symphysis pubis,
which is covered with hair after puberty.
Labia majora: Two large outer ‘lips’ of fatty tissue that run down
both sides of the vulva from the mons pubis to the perineum.
They protect the entrance to the vagina and urethra.
Labia minora: Two smaller folds of skin within the labia majora,
which surround the clitoris to protect it similar to the male
prepuce.
Clitoris: Just like a very small penis, sensitive and containing
erectile tissue. It is situated just below the mons pubis. The
erectile tissues fill with blood and swell up during sexual
intercourse.
7