The document discusses human reproduction and provides details about: 1) The male and female reproductive systems, including structures like the testes, ovaries, uterus, and their functions. 2) Gamete formation - sperm in males which are produced in the testes, and eggs in females which develop in the ovaries. 3) The process of puberty, where sex hormones trigger sexual maturation and development of secondary sexual characteristics between ages 12-14.

1. IGCSE BIOLOGY
SECTION 3 LESSON 2

2. Content
Section 3
Reproduction
and
Inheritance
a) Reproduction
- Humans

3. Content
Lesson 2
a) Reproduction –
Humans
Humans
3.8 describe the structure and explain
the function of the male and female
reproductive systems
3.9 understand the roles of oestrogen
and progesterone in the menstrual cycle
3.10 describe the role of the placenta
in the nutrition of the developing
embryo
3.11 understand how the developing
embryo is protected by amniotic fluid
3.12 understand the roles of oestrogen
and testosterone in the development of
secondary sexual characteristics

4. Human gametes (sex cells)

5. Human gametes (sex cells)
Male sex cell = sperm

6. Human gametes (sex cells)
Male sex cell = sperm

7. Human gametes (sex cells)
Male sex cell = sperm
Head
Tail
The chromosomes (genetic
information) are tightly packed
together in the nucleus

8. Human gametes (sex cells)
Male sex cell = sperm
Head
Tail
The chromosomes (genetic
information) are tightly packed
together in the nucleus
The tail lashes from side to side
and propels the sperm forwards

9. Human gametes (sex cells)
Male sex cell = sperm
Head
Tail
The chromosomes (genetic
information) are tightly packed
together in the nucleus. Acrosome
is a vesicle containing enzymes, to
disslove a way through the jelly
surrounding the egg cell.
The tail lashes from side to side and
propels the sperm forwards.
Tail same with flagellum is a long
whip-like tail structure found on
sperm used for swimming
A single ejaculate may be about
4cm3 of fluid and may contain up to
500 million sperms

10. Human gametes (sex cells)
Female sex cell = egg (ovum)
Membrane
Nucleus containing
chromosomes
Cytoplasm
Jelly coat

11. Human gametes (sex cells)
Egg begin to be formed inside a girl’s ovaries before she is born. At birth,
she will already have thousands of partly developed eggs inside her ovaries.
An egg is a single cells. When it fully developed, it burst out of the ovary
and into the funnel at the end of the oviduct. This is called Ovulation
Membrane
Nucleus containing
chromosomes
Cytoplasm
Jelly coat

12. Summary of sexual development
MALE FEMALE
AT BIRTH Testes have descended into scrotal
sac but they do not make sperms yet
Ovaries containing immature eggs
present in abdomen but they do not
produce eggs yet
12-14 years
PUBERTY
45-50
70-75

13. Summary of sexual development
MALE FEMALE
AT BIRTH Testes have descended into scrotal
sac but they do not make sperms yet
Ovaries containing immature eggs
present in abdomen but they do not
produce eggs yet
12-14 years
PUBERTY
PITUITARY GLAND
Gonad-stimulating hormones
Testes
Male sex hormones (androgens)
Testes start producing sperms.
Secondary sexual
characteristics, eg growth of
body hair, breaking of voice
PITUITARY GLAND
Gonad-stimulating hormones
Ovaries
Female sex hormones
(oestrogens)
Ovaries start producing eggs.
Secondary sexual
characteristics, eg. growth of
breasts, fat in thighs
45-50
70-75

14. Summary of sexual development
MALE FEMALE
AT BIRTH Testes have descended into scrotal
sac but they do not make sperms yet
Ovaries containing immature eggs
present in abdomen but they do not
produce eggs yet
12-14 years
PUBERTY
PITUITARY GLAND
Gonad-stimulating hormones
Testes
Male sex hormones (androgens)
Testes start producing sperms.
Secondary sexual
characteristics, eg growth of
body hair, breaking of voice
PITUITARY GLAND
Gonad-stimulating hormones
Ovaries
Female sex hormones
(oestrogens)
Ovaries start producing eggs.
Secondary sexual
characteristics, eg. growth of
breasts, fat in thighs
45-50 MENOPAUSE
Ovaries stop producing eggs
70-75

15. Summary of sexual development
MALE FEMALE
AT BIRTH Testes have descended into scrotal
sac but they do not make sperms yet
Ovaries containing immature eggs
present in abdomen but they do not
produce eggs yet
12-14 years
PUBERTY
PITUITARY GLAND
Gonad-stimulating hormones
Testes
Male sex hormones (androgens)
Testes start producing sperms.
Secondary sexual
characteristics, eg growth of
body hair, breaking of voice
PITUITARY GLAND
Gonad-stimulating hormones
Ovaries
Female sex hormones
(oestrogens)
Ovaries start producing eggs.
Secondary sexual
characteristics, eg. growth of
breasts, fat in thighs
45-50 MENOPAUSE
Ovaries stop producing eggs
70-75 Testes stop making sperms

16. Male and female reproductive
systems

17. Male and female reproductive
systems

18. Male and female reproductive
systems

19. Male reproductive system
TESTES (singular
testis). Sperms are
manufactured here.
The testes are
slightly cooler than
the rest of the body.

20. Male reproductive system
SCROTAL SAC (or
scrotum). Alters
position to maintain
the optimum
temperature for the
testes.

21. Male reproductive system
SPERM TUBULES –
where the sperm are
actually made.
Combined length of
over 500 metres!

22. Male reproductive system
EPIDIDYMIS –
coiled tube where
the sperm are stored

23. Male reproductive system
URETHRA – tube
which runs down the
centre of the penis –
dual function,
carrying both urine
and sperms

24. Male reproductive system
PENIS – male
reproductive organ.
During intercourse
it fills with blood to
become stiff and
erect. Tip of the
penis, the GLANS, is
protected by the
foreskin.

25. Male reproductive system
SEMINAL VESICLE
and PROSTATE
GLAND – these
glands produce a
fluid which keeps the
sperm alive and
swimming vigorously.
Sperm + fluid =
semen

26. Male reproductive system

27. Female reproductive system
OVARIES (singular
ovary). Two, on
either side of the
abdomen. Every 28
days or so an egg is
released.

28. Female reproductive system
OVIDUCTS (also
known as the
Fallopian tubes)
carry the eggs from
the ovaries to the
uterus. Fertilisation
occurs here.

29. Female reproductive system
UTERUS – if the egg is
fertilised by the sperm,
then it develops here
into the baby during
which time it is known
as the womb). This has
very thick walls, made
of muscle. It is quite
small-only about the
size of clenched first-
but it can stech a great
deal when a woman is
pregnant

30. Female reproductive system
CERVIX – the neck
of the uterus.
Becomes dilated
(opens up) just prior
to the birth of the
baby.

31. Female reproductive system
VAGINA – the birth
canal. Like the lining
of the uterus, the
vagina secretes a lot
of mucus.

32. Female reproductive system
CLITORIS – the
female equivalent of
the penis, can
become erect during
sexual intercourse

33. Female reproductive system