Secondary 4 Sexual Reproduction in Humans

1. Reproduction
Issues on Sex

2. lessonOBJECTIVES
• Define asexual reproduction as the process resulting
in the production of genetically identical offspring
from one parent
• Define sexual reproduction as the process involving
the fusion of nuclei to form a zygote and the
production of genetically dissimilar offspring
• Identify on diagrams, the male reproductive system
and give the functions of: testes, scrotum, sperm
ducts, sex glands, urethra and penis
• Identify on diagrams, the female reproductive
system and give the functions of: ovaries, oviducts,
uterus, cervix and vagina

3. lessonOBJECTIVES
• Briefly describe the menstrual cycle with reference to
the roles of oestrogen and progesterone only
• Briefly describe different methods of birth control
• Evaluate the consequences and issues relating to
premarital sex
• Evaluate the consequences and issues relating to
abortion
• State the harmful consequences of sexually
transmitted infections (STIs)
• State how STIs can be prevented

4. All about gametes
• Gametes are produced in reproductive
organs call gonads
– Male gonads  Testes (produce sperms)
– Female gonads  Ovaries (produce
ova/eggs)
• Gametes have half the chromosome
number as the normal body cells
– Eg. Cheek cell – 46, egg/sperm – 23
– Normal body cell produced by mitosis
– Gametes produced by meiosis

5. Why gametes have half the
chromosomes numbers?
• Sexual reproduction involves fusion of
2 gametes (fertilisation)
• When egg fuses with sperm, zygote is
formed
– Chromosome number is restored.
– Eg egg(23) fuse with sperm(23) =
zygote(46)
• Normal chromosome number is called
diploid number (2n)
• Half the chromosome number is
called haploid number (n)

6. reproductionOVERVIEW
• Reproduction is necessary to ensure the
continuity of species- organisms must produce
new organisms like themselves
• The production of new organisms is called
reproduction
• There are two types of reproduction:
• Sexual Reproduction
• Asexual Reproduction

7. • Asexual reproduction is defined as the
process resulting in the production of
genetically identical offspring from one
parent without the fusion of gametes (sex
cells)
• Sexual reproduction is defined as the process
resulting in the production of genetically
dissimilar offspring from one or two parents,
involving the fusion of gametes to form a
zygote.
• Gametes are sex cells that are produced in
reproductive organs called gonads.
reproductionOVERVIEW

8. Male Reproductive System

9. Male Reproductive System –
Front View

10. Male Reproductive System –
Side View

11. Functions of Male
Reproductive Parts
Organ Function
Testes Produce sperms and hormone testosterone.
Scrotum Holds the testes outside the body where temperature is
lower than inside the body and most suitable for
production and storage of sperm.
Sperm duct Transports sperm to the penis.
Prostate gland Secretes fluid which mixes with the sperms. This fluid
contains nutrients and enzymes which nourish the sperms
and activate them to swim.
Urethra Carries both urine and semen, at different times.
Penis Deposits semen into the vagina of the female.

12. Female Reproductive System
– Front View

13. Female Reproductive System
– Side View

14. Functions of Female
Reproductive Parts
Organs Function
Ovaries Produce eggs and female sex hormones
(oestrogen and progesterone)
Oviducts Narrow muscular tube from the ovary to the uterus.
Site of fertilisation.
Uterus
(womb)
Place where the embryo is implanted and the
foetus develops during pregnancy
Cervix Narrow opening that enlarges during birth to allow
the passage of the foetus
Vagina
(birth
canal)
Place where semen is deposited during sexual
intercourse

15. Puberty
• Stage of human growth and development in
which a person becomes physically mature
• Begins at about 11 for girls, 14 for boys
• Secondary sexual characteristics formed
– Eg. Reproductive system begin to function
– Sex organ matures and produces gametes
• Changes are brought about by sex hormone
– Female sex hormones: oestrogen and
progesterone
– Male sex hormone: testosterone

16. Menstrual cycle

17. Menstruation
Repair
of
uterine
lining
Thickening
of uterine
lining
Oestrogen
Progesterone

18. http://course.zju.edu.cn/532/study/theory/2/Genital%20system/M
enstrual%20cycle.swf

19. Phases of Menstrual Cycle
• Day 1 to 5 :
– Uterine lining (endometrium) breaks down
– Broken lining and unfertilised egg is being
discharged via the vagina.
• Day 6 to 13 :
– Oestrogen is secreted
– Effects of oestrogen
• Repair and growth of uterine lining
(become thick)
• Supply the uterine lining with blood vessel

20. Phases of Menstrual Cycle
• Day 14 :
– Matured egg is released from the ovary into the
oviduct.
– Fertile period: The period when fertilization is
possible which is usually 3 days after and 3 days
before ovulation. This is because after the egg’s
release from an ovary, it can only survive for
one or two days. Sperms can live for two to
three days in the female reproductive system.
• Day 15 to 28 :
– Progesterone is secreted which helps to
maintain uterine lining and cause it to further
thickens, supplied with more blood vessel
(preparing it for fertilised egg to implant)

21. sexualINTERCOURSE

22. sexualINTERCOURSE
• The (erect) penis is inserted into the vagina
during sexual intercourse
• Millions of sperms are released from the penis
and deposited into the vagina
• Sperms swim from the vagina, pass the cervix,
up the uterus and into the fallopian tubes;
many sperms die before reaching the
fallopian tubes

23. sexualINTERCOURSE
• If a sperm meets an egg in the fallopian tube,
fertilisation occurs
• Fertilisation is the fusion of the nucleus of the
sperm with the nucleus of the egg to form a
zygote
• The zygote then divides to form a small ball of
cells which moves towards the uterus for
implantation
Video Link

24. • If a sperm meets an egg in the
fallopian tube, fertilisation occurs
• Fertilisation is the fusion of the nucleus
of the sperm with the nucleus of the
egg to form a zygote
• The zygote then divides to form a small
ball of cells which moves towards the
uterus for implantation
sexualINTERCOURSE

25. What happens if fertilization
does not take place?
– Egg will break down.
– Progesterone stops secreting
– Uterine lining breaks down.
– Menstruation occurs.
– The cycle repeats

26. What happens if fertilisation
does take place?
– The male penis deposited semen into
the female vagina.
– The sperms swim up the uterus into
the oviducts or the fallopian tube.
– At the fallopian tube, the nuclei of
the sperm and the ovum fuse
together.
– Sperm + Ovum → Zygote

27. When a woman is going to have a baby, she is said to be pregnant.
A pregnancy lasts for about 38 weeks (9 months).
•During implantation, the
embryo reaches the
uterus and attaches
itself onto the wall of the
uterus. Cell division
continues.
Embryo Development

28. •After the placenta develops in the
wall of the uterus, the embryo joins
to via an umbilical cord.
•The embryo receives food and
oxygen from the mother and pass
waste substances back through the
umbilical cord and placenta.
•The placenta also stops infections
and harmful substances from
reaching the embryo. A surrounding
liquid also protects the embryo.
Embryo Development

29. umbilical
cord
placenta
vagina
Embryo Development

30. y

31. i. Acts as a shock
absorber to protect the
foetus against
mechanical injury.
ii. Buoys up the foetus to
allow it to move freely
during growth.
iii. Helps to lubricate and
reduce friction in the
vagina.
Amniotic Fluid

32. Fetal Development (1st month)

33. Fetal Development (9th month)
http://www.babycentre.co.uk/pregnancy/fetaldevelopment/

34. Function of amniotic sac
and amniotic fluid
• Supports and cushions the fetus
before birth.
• Absorbs shock, if the mother falls.
• Protects the baby against physical
injury.
• During birth, it lubricates and
reduces friction in the vagina.
• Allows fetus to move freely.
[PURE]

35. Function of Placenta and
Umbilical Cord
• Allows oxygen and dissolved food
substances to diffuse from the mother’s
blood into the fetus’s blood.
• Allows excretory products such as urea and
carbon dioxide to diffuse from fetus to
mother.
• Allows protective antibodies to diffuse from
mother to fetus.
[PURE]

36. i) Umbilical
Arteries
ii) Umbilical
Veins

37. Umbilical Cord consists of
Type of Blood
Vessels:
Functions:
i) Umbilical
Arteries
Carry deoxygenated blood and
metabolic waste products (e.g
urea) from fetus to the placenta.
ii) Umbilical Vein Transports oxygenated blood and
nutrients from the placenta to the
fetus.

38. sexISSUES

39. birthCONTROL
• Sex is an intimate act between a man and a
woman.
• Often, married couples have children birthed
out of their love.
• However, sometimes they choose not to have a
child immediately.
• Family Planning is when couples plan when to
have a baby and how many to have.
• Contraception is a measure used to prevent
unwanted pregnancies by applying one or
more of the following methods:

40. rhythmMETHOD
• Rhythm Method (Natural Method)
– A couple times their intercourse to
avoid the fertile period in a woman’s
menstrual cycle
– Fertile period refers to the period
where ovulation has likely occurred

42. Condom
– This is a thin rubber tube
– Males put this on their erect penis before
sexual intercourse
– The condom is a barrier that prevents the
sperms from meeting the egg. Most
condoms have a coating of spermicide.
– It is also impermeable to germs like
bacteria and viruses.
– Hence, the condom can also minimise the
risk of contracting sexually transmitted
infections
– Female versions of the condom can also
be used

44. Spermicide
• Substances that kill sperms
• Can be creams, jellies, foam or tablets
• A woman applies spermicide into her
vagina before intercourse
• Can be applied on condoms, caps or
diaphragms as well

46. Cervical Cap and Diaphragm
• This is fitted over the cervix to prevent
sperms from entering the uterus.
• It can be used together with
spermicides to kill the sperms

48. Intra-Uterine Device (IUD)
• A T-shaped plastic with a copper
wire coiled around it
• It is inserted into the uterus by a
doctor
• It prevents the implantation of the
embryo onto the uterine lining.

50. Oral Contraceptive Pills
(Birth Control Pills)
• There are hormonal pills that prevent
ovulation and thus prevent pregnancy
• They have to be taken regularly and
follow a strict regimen
• You can only obtain these from a
doctor

53. Permanent Contraceptive
Methods
• Permanent contraceptive methods are
done by a doctor
• This method is also known as sterilisation
and is irreversible. It makes the person
incapable of reproducing
• This method should only be done if the
couple has decided not to have any
more children

54. Vasectomy (Males)
• The sperm ducts are cut and tied
• This prevents sperms from being
released through the penis

55. Ligation (Females)
• The fallopian tubes are cut and tied
• This prevents the ova from reaching the
uterus

56. premaritalSEX
• When a couple engage in sex before they are
married, it is known as pre-marital sex.
• Pre-marital sex can result in:
– Unwanted or unplanned pregnancy
– Contracting sexually transmitted infections
– Abortion
• An abortion is the deliberate termination of a
pregnancy.
• An abortion is NOT a method of contraception
since the sperm has already fertilised the egg.

57. Dangers of an Abortion
Physical health problems Mental health
problems
Uterus and oviducts may
become infected, resulting in
sterility (infertility)
Sharp instruments may
puncture the uterus, resulting
in excessive blood loss
Excessive blood loss may
lead to death of the mother
Depression
Suicidal tendencies
Sense of loss
Sense of guilt

58. abortion

59. abortion
2 months

60. abortion
3 months

61. abortion
4 months

62. abortion
6 months

63. abortion
7 months

64. abortion
How do YOU feel about these reasons?
“This pregnancy was an
accident. My boyfriend
and I are not yet married.”
“I already have five
children and cannot
afford another one.”
“This is an ectopic pregnancy and could cost my
wife her life.”
“The child is found to be severely deformed and
does not have a high chance of survival.”
“I was raped.”
“The foetus is too young to feel pain.”

65. Sexually Transmitted Infections
• Sexually transmitted infections (STIs) are
diseases that are spread from one person to
another through sexual intercourse
• Common STIs include
– gonorrhoea
– syphilis
– AIDS (acquired immunodeficiency
syndrome)

66. Prevention of STIs
• STIs can be prevented in the following ways:
– Stick to one unaffected sex partner and
avoid sexual promiscuity
– Abstain from premarital sex
– Avoid direct contact between the penis
and the vagina by using a condom
– Do not share used instruments (needles,
blades) that can break the skin (eg. drug
abuse, ear piercing, tattooing equipment,
etc)
– Increase public awareness through
campaigns and sex education