Ch.6.reproduction in humans

1 of 40 © Boardworks Ltd 2008

Puberty: Body changes &
differences
© Changing Faces 2009 Registered Charity No. 1011222 Charity registered in Scotland SC039725

What happens during puberty?
Humans are born with a complete set
of sex organs. However, they do not
usually become active until between
the ages of 10 and 18.
In males, the testes start to make
sperm, and in females, the ovaries
start to release eggs.
This stage of development is called
puberty, and is caused by hormones.
During this important time, many
changes take place in the bodies
of young men and women.

Hormones
Hormones are chemicals that are
produced in one part of the body,
circulates all round the body in the blood
but only has an effect on a specific part
of the body.
At the age of 10 – 13 in girls and 12 – 14
in boys, the pituitary glands (beneath
the brain) secrete growth hormones
and gonadotropin.
Gonadotropin stimulates the production
of sex hormones.

In females the sex hormones produced
are oestrogen and progesterone
(produced in the ovaries).
In males the sex hormones produced is
testosterone (produced in the testicles).
The sex hormones cause the sex organs
to develop fully.
They work with the growth hormones
and cause the body to develop
(secondary sexual characteristics)

• What is puberty?
• What changes can we expect?
• A look at the differences between
girls and boys and amongst each
other
What this lesson will cover…What this lesson will cover…

What is puberty?
• PubertyPuberty is the time in life when you begin to become
an adult. This means a lot of changing and growing –
both inside and out.
• Some of the changes that happen in puberty are also
known as adolescenceadolescence..
• Puberty starts because of sex hormonessex hormones (chemicals in
our bodies that send messages about our
development).
• In adolescence a person also develops adult emotions
and social skills.

Changes in boys
• Growth of PenisPenis & testestestes (size)
• Body & facial hair
• Pubic hairPubic hair (the hair around sex organs)
• Shoulders grow wider
• Voice change (or voice breaking)
• Body odourBody odour (smell) & acneacne (spots)

Changes in girls
• Breast development
• Body hair (e.g. on legs, arms,
underarms) & pubic hairpubic hair (the hair around our
sex organs)
• MenstruationMenstruation (a monthly bleed or period)
• Hips grow wider
• Body odourBody odour (smell) & acneacne (spots)

What is reproduction?
Reproduction is one of the
seven life processes.
Humans use sexual
reproduction to
produce their young.
In order to do this, the two
parents (male and female)
have different reproductive
systems and organs that
produce different sex cells.
All living things reproduce.

Sex cells
Sperm cell (Male) Egg cell (Female)
The main function of a sperm cell is
to FERTILISE the egg cell and pass
on the genetic information (DNA)
needed to make a baby
The main function of an egg cell is
to join with a SPERM CELL
(fertilisation) and pass on the
genetic information (DNA) needed to
make a baby

Sex cells – sperm
Sperm are produced in sex organs called testes.
In males, the sex cells are called sperm.
headtail middle piece
cell membrane nucleus containing
DNA

Sex cells – egg
Eggs are produced in sex organs called ovaries.
In females, the sex cells are called eggs.
nucleus containing
DNA
membrane jelly coat
cytoplasm

Penis and testicles Penis
is a cylindrical shaped organ
filled with ‘spongy tissue’.
Testicles
Males are born with a pair of
testicles. Sperm cells are
made inside them.
On its own, sperm is actually
like jelly. Each testicle is
connected to a gland. These
add a pale white fluid to the
sperm called semen.

Glands
The sperm must be mixed
with a fluid called semen so
that it can flow freely. This
semen is made inside the
glands.
The semen also helps to
nourish the sperm so it can
stay alive during its journey to
the egg.
Fact
Men who have had their
testicles severely damaged or
removed still ejaculate.
Q. Will they still be able to
fertilise an egg cell?
Glands

Scrotum
Scientific Description
The scrotum is a sack of skin
that protects the testicles.
When a man is cold, the
scrotum tightens up pulling
the testicles closer to the
body.
When a man is hot, the
scrotum relaxes to allow the
testicles to hang further away
from the body.
Q. How does this protect
the sperm?

Sperm Ducts
The sperm is carried away
from the testicles through the
sperm ducts. These tubes take
the sperm to the glands where
they are mixed with semen.

Prostate
The prostate is a gland that
acts like a pump. During
ejaculation the prostate mixes
the semen and sperm together,
then pumps it out the end of
the penis.

Urethra
Scientific Description
The urethra is a tube that runs
down the centre of the penis.
The semen and sperm mixture
flows out the end of the urethra
when a man ejaculates.
The urethra is not only used for
sexual intercourse. It also
carries urine from the bladder
when a man urinates.

The male reproductive system

Female reproductive system
The two ovaries
contain hundreds of
undeveloped female
sex cells called egg
cells or ova.
Women have these
cells in their bodies
from birth - whereas
men produce new
sperm continually.

Oviduct or Fallopian tube.
Oviduct or Fallopian
tube is lined
with cilia, which are
tiny hairs on cells.
Every month, an egg
develops and
becomes mature, and
is released from an
ovary. The cilia waft
the egg along inside
the egg tube and into
the uterus.

Uterus
The uterus is also
called the womb. It is
a muscular bag with a
soft lining. The uterus
is where a baby
develops until its birth.

Cervix
The cervix is a ring of
muscle at the lower
end of the uterus. It
keeps the baby in
place while the
woman is pregnant.

Vagina
The vagina is a
muscular tube that
leads from the cervix
to the outside of the
woman's body.

The female reproductive system

Male or female?

Roles of the reproductive system

Sperm or egg?

Menstruation
An important part of puberty for girls is the beginning of
their monthly cycle. This is known as the menstrual cycle.
The menstrual cycle
involves the preparation of
the uterus lining so that it
can receive a fertilized egg.
If an egg is fertilized, it can
implant itself in the prepared
uterus lining.
If the egg is not fertilized, the lining of the uterus
breaks down and is lost from the body. This is called
menstruation, or a period.

Periods

What is fertilization?
Fertilization is the fusing of an egg and a sperm cell. In this
process the sperm’s nucleus will join with the egg’s nucleus.
For a woman to become pregnant fertilization must occur.
Females produce an egg
approximately every 28 days.
This is called ovulation.
Males continually produce
sperm in the testes.
How do these cells come into close contact with each other?

Sexual intercourse
During sexual intercourse
the man inserts his penis
into the woman’s vagina.
Millions of sperm cells are
ejaculated into the top of
the vagina.
They enter the uterus through
the cervix, where the sperm
cells may meet an egg.
Now fertilization can occur.

Fertilization and implantation

Reproduction terms

The placenta
How does an embryo receive food and oxygen and how
does it get rid of waste?
An embryo forms a structure called the placenta, which
attaches to the uterus wall.
The umbilical cord joins
the fetus to the placenta.
In the placenta, food and oxygen
diffuse from the mother’s blood
into the blood of the fetus.
Carbon dioxide and waste
products diffuse from the blood of
the fetus into the mother’s blood.
umbilical
cord

How does the placenta work?

From embryo to fetus
In the earliest stages of development, a human baby is
called an embryo.
After the first eight weeks of pregnancy, a human embryo
is then called a fetus.
At this stage, the fetus has all the main human features.
The fetus continues to
develop and grow inside
its mother’s uterus for a
total of 40 weeks.

What are the stages of development?

The stages of pregnancy

Birth
After 40 weeks of gestation, the baby
is ready to be born. At this point, the
head usually lies just above the cervix.
Eventually the contractions cause the amnion to break and
the fluid escapes.
1st
- Birth begins with small
contractions (30 min. apart) of the
uterus wall (12 – 14 hrs), which
gradually become stronger and more
frequent (2 – 3 min. apart).

After a few minutes, the placenta comes away from the
uterus wall. This is pushed out as the afterbirth.
The cervix then widens and dilates as
the baby is pushed through the vagina.
2nd
– Mother contracts her abdominal
muscles with the uterus contractions
to push the foetus down.

What are contraceptives?
Contraceptives are devices designed to prevent pregnancy.
Sexually transmitted infections are
diseases that can be passed on by
sexual contact.
How do the different types of contraceptives work?
Contraceptives are not 100% reliable
and some can cause other side effects.
Some types of contraception can also
stop the spread of sexually
transmitted infections.

Different types of contraceptives
 Condoms – a latex barrier worn
over an erect penis. This barrier
prevents sperm entering the
vagina and causing pregnancy.
It can also help to stop the spread
of sexually transmitted infections.
 Contraceptive pill – a pill containing a mixture of
hormones taken every day. These hormones stop the
release of eggs, preventing pregnancy. However the pill
cannot protect against disease.
 Diaphragm and cap – these are barriers inserted into
the vagina to prevent sperm reaching the egg.

Alternatives to contraception
Some people in long term relationships choose to use
natural family planning instead of contraceptives.
This involves working out
when the woman is fertile
and avoiding sexual
intercourse at these times.
This method does not
have any effect on the
body, but it can be an
unreliable form of birth
control and does not
protect against sexually
transmitted infections.

Emergency contraception
Emergency contraception is available to women that
have had unprotected sex, to prevent pregnancy.
This is in the form of a
pill, often called the
‘morning after pill’. It
should be taken within 3
days of unprotected sex,
in order to be effective.
However, it does not protect against sexually
transmitted diseases and it can have side effects.

Which contraceptive?

Sexually transmitted infections

HIV and AIDS

Glossary

Anagrams

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Ch.6.reproduction in humans

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