The male reproductive system
Structures of the male reproductive system
The male reproductive system has several key components
The structure and function of these components can be seen in the table below
Structure Function
Prostate
Produces fluid called semen that provide sperm cells with nutrients
gland
Sperm passes through the sperm duct to be mixed with fluids produced by the glands before
Sperm duct
being passed into the urethra for ejaculation
Tube running down the centre of the penis that can carry out urine or semen, a ring of
Urethra
muscle in the urethra prevents the urine and semen from mixing
Contained within a bag of skin (scrotum) and produces sperm (male gamete) and
Testis
testosterone hormone
Sac supporting the testes outside the body to ensure that sperm are kept at a temperature
Scrotum
slightly lower than body temperature
Passes urine out of the body from the bladder and allows semen to pass into the vagina of a
Penis
woman during sexual intercourse
The male reproductive system diagram
The male reproductive system
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The female reproductive system
Structures of the female reproductive system
The female reproductive system has several key components
The structure and function of these components can be seen in the table below
Structure Function
Connects the ovary to the uterus and is lined with ciliated cells to push the released ovum
Oviduct
down it. Fertilisation occurs here
Ovary Contains ova (female gametes) which will mature and develop when hormones are released
Muscular bag with a soft lining where the fertilised egg (zygote) will be implanted to develop
Uterus
into a foetus
Ring of muscle at the lower end of the uterus to keep the developing foetus in place during
Cervix
pregnancy
The muscular tube that leads to the inside of the woman's body where the males penis will
Vagina
enter during sexual intercourse and sperm are deposited
The female reproductive system diagram
The female reproductive system
Gametes & Fertilisation
What is fertilisation?
Fertilisation is the fusion of the nuclei from a male gamete (sperm cell) and a
female gamete (egg cell)
It occurs in the oviducts
Gametes have adaptations to increase the chances of fertilisation and
successful development of an embryo
Fertilisation diagram
The sperm enters the egg cell during fertilisation which usually occurs in the
oviduct
Adaptations of Gametes
Human gametes
The human gametes are the egg and the sperm cells
Egg and sperm cell diagram
Comparing sperm and egg cells
Adaptive features of the gametes
The gametes are highly specialised cells with adaptive features designed to
maximise the chances of successful reproduction
These adaptive features are compared in the table below
Gamete Adaptive feature Function
has a flagellum (tail) allows the sperm to swim towards the egg
contains enzymes in the head region
Sperm to digest a route into the egg for fertilisation
(acrosome)
contains many mitochondria to provide energy for movement of the flagellum
to provide energy for cell division in the developing
cytoplasm contains a store of energy
zygote after fertilisation
Egg
jelly-like coating that changes after to make an impenetrable barrier after fertilisation to
fertilisation prevent more sperm entering the egg
Comparison of Male & Female Gametes
Comparative
Sperm Egg
Feature
Size Very small (45 µm) Large (0.15 mm)
Head region, flagellum, many Round cell with few structure adaptations,
Structure
structural adaptations covered in a jelly coating
Motility Capable of locomotion Not capable of locomotion
Produced every day in huge numbers Thousands of immature eggs in each ovary,
Numbers
(around 100 million per day) but only one is released each month
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Pregnancy: growth & development of the fetus
After fertilisation in the oviduct, the zygote travels towards the uterus
o This takes about 3 days, during which time the zygote will divide several
times to form a ball of cells known as an embryo
In the uterus, the embryo embeds itself in the thick lining (implantation) and
continues to grow and develop
The gestation period for humans is 9 months
o Major development of organs takes place within the first 12 weeks,
during which time the embryo gets nutrients from the mother by diffusion
through the uterus lining
o After this point the organs are all in place, the placenta has formed and
the embryo is now called a fetus
o The remaining gestation time is used by the fetus to grow bigger in size
The fetus is surrounded by an amniotic sac which contains amniotic
fluid (made from the mother’s blood plasma)
o This protects the fetus during development by cushioning it from
bumps to the mother’s abdomen
The umbilical cord joins the fetus’s blood supply to the placenta for exchange
of nutrients and removal of waste products
The fetus in the uterus
The placenta & umbilical cord: extended
What is the the placenta and the umbilical cord?
During the gestation period the fetus develops and grows by gaining
the glucose, amino acids, fats, water and oxygen it needs from the mother’s
blood
The bloods run opposite each other, never mixing, in the placenta
The fetus’s blood connects to and from the placenta by the umbilical cord
The mother’s blood also absorbs the waste from the fetus’s blood in the
placenta; substances like carbon dioxide and urea are removed from the fetus’s
blood so that they do not build up to dangerous levels
Movement of all molecules across the placenta occurs by diffusion due
to difference in concentration gradients
The placenta is adapted for this diffusion by having a large surface area and
a thin wall for efficient diffusion
Toxins and pathogens
The placenta acts as a barrier to prevent toxins and pathogens getting into the
fetus’s blood
Not all toxin molecules or pathogenic organisms (such as viruses,
eg rubella) are stopped from passing through the placenta (this usually depends
on the size of the molecule)
This is why pregnant women are advised not to smoke during pregnancy as
molecules like nicotine can pass across the placenta
Placenta and umbilical cord diagram
The placenta
