Transcript Reproduction in Humans

Reproduction in Humans
(f) identify on diagrams of the male reproductive system and give the
functions of: testes, scrotum, sperm ducts, prostate gland, urethra
and penis
(g) identify on diagrams of the female reproductive system and give
the functions of: ovaries, oviducts, uterus, cervix and vagina
(h) briefly describe the menstrual cycle with reference to the
alternation of menstruation and ovulation, the natural variation in
its length, and the fertile and infertile phases of the cycle, with
reference to the roles of estrogen and progesterone only
(i) briefly describe fertilisation and early development of the zygote
simply in terms of the formation of a ball of cells which becomes
implanted in the wall of the uterus
(j) discuss the spread of human immunodeficiency virus (HIV) and
methods by which it may be controlled
Male Reproductive System
seminal vesicle
sperm duct
prostate gland
urethra
penis
testis
scrotum
Front view
Male Reproductive System
prostate gland
seminal vesicle
penis
urethra
testis
Left side view
scrotum
Male Reproductive System
Parts
Function
Testes
Produce sperms
Produce male hormones, such as testosterone
Scrotum
Support and protect the testes.
It’s at slightly lower temperature for normal
development of sperm
Seminal vesicle
Store sperms temporarily
Sperm ducts
Transport sperms to the urethra in preparation for
ejaculation
Prostate gland
Contains fluid which is rich in nutrients and enzymes
to nourish the sperms and activate them
Urethra
Carries semen and urine to outside of the body
Penis
Enter the vagina of a woman during sexual
intercourse to deposit semen
Male Reproductive System
Sperm
• Produced in testis
• Millions are released during ejaculation
• Swim around in semen
• Head: contain nucleus, with haploid set of
chromosome
• Tail: Beating movement of tail enables it to swim
• Path taken by sperm during ejaculation
Testis  sperm duct  urethra  deposited in vagina
Female Reproductive System
oviduct
ovary
uterus
uterine lining
cervix
vagina
vulva
Front view
Female Reproductive System
oviduct
ovary
uterine lining
cervix
uterus
vagina
Left side view
vulva
Female Reproductive System
Parts
Ovaries
Oviducts/
fallopian tube
Uterus
Cervix
Vagina
Function
Produces eggs
Produces female sex hormones such as
oestrogen and progesterone.
where egg is fertilised
where the fetus or unborn baby develops
during pregnancy
enlarges to allow passage of the fetus
during birth
Where semen is deposited during sexual
intercourse
Female Reproductive System
Egg/ Ovum
• Produced by ovary
• Only 1 mature egg is released into oviduct
after menses in the menstrual cycle
Sperm VS Egg
Sperm
Egg
Produced by testes
Produced by ovaries
Small
Larger than sperm
Millions are released
Only one is released monthly
Has a tail to enable it to swim
Cannot move by itself
Menstrual Cycle
1 Menstrual flow stage
(Day 1–5)
oestrogen causes uterine
lining to grow and thicken
Follicle stage
2 (Day 6–13)
repair of
uterine lining
menstruation
progesterone causes
uterine lining to thicken
further and become
well-supplied with
blood, preparing it for
the fertilised egg.
Ovulation
3 (Day 14)
Corpus luteum stage
4 (Day 15–28)
Menstrual Cycle
1.
Menstrual flow stage
Breakdown of uterine lining and discharged through the vagina
2. Follicle stage
- Oestrogen secreted for repair and build of uterine lining
- Ovary produce eggs
3. Ovulation
Ovulation day/Most fertile day: day 14
Mature egg released into oviduct
Progesterone secreted to maintain thickness of the uterine lining
and ensure it is well-supplied with blood vessels. This prepare the
uterus for implantation of zygote if fertilisation is successful.
4. Corpus luteum stage
When there is no fertilisation, less progesterone secreted. Hence,
uterine lining thickness is no longer maintained and breaks down.
Concentration of
hormones in blood
Menstrual Cycle
Thickness of
uterine lining
Oestrogen
oestrogen
Progesterone
progesterone
uterine lining grows
and thickens
5
menstruation
14
ovulation
28
5
Days
Menstrual Cycle
• Fertile period: Day 11 to 16
• Infertile period: remaining days
• Why is fertile period longer than just the day
of ovulation: Sperm can survive up to 2days so
en egg released two days after sexual
intercourse can still be fertilised.
• Factors affecting length of menstrual cycle:
Stress, Unbalanced diet, Mental fatigue, Illness,
Malnutrition
Given a 28-day menstrual cycle,
• Date of end of menstruation: X + 4
• Date of ovulation: X + 13
• Date of next cycle: X + 28
Example:
• Susan had her first day of menses on 3 Jan.
(a) When would she expect bleeding to end: 7 Jan (Day 5)
(b) When is the most fertile day: 16 Jan (day 14)
(c) Next first day of menses: 31 Jan (28 days later)
(d) Which dates fall within infertile period: 13 Jan to 18 Jan
(day 11 to day 16)
Fertilisation
• Fertilisation: Fusion of male nucleus in sperm
with female nucleus in egg to form a zygote
• After sexual intercourse, sperms are deposited in
the vagina. The sperms swim up the uterus and
move into the oviduct. A sperm will enter the egg
to fertilise it.
• Egg + sperm  Zygote  Embryo
• Implantation: Embryo moves down from oviduct
to uterus, where it embeds itself into the uterine
lining.
HIV/ AIDS
HIV is spread by transfer of blood from an infected
person to a non-infected person
Transmission:
• sexual intercourse with an infected person.
• sharing a needle with an infected person e.g.
• when drug addicts share their needles
• Unsterilised needles used for tattooing,
acupuncture or ear-piercing
• blood transfusion with blood from an infected
person.
• Infected mothers to their babies during and after
birth (breastfeeding)
HIV/ AIDS
Prevention and control
• Have only one sex partner in a lifetime
• Use condom during sexual intercourse
• Avoid sharing of instruments that may be
contaminated with blood
• Avoid drug abuse as drug addicts tend to
share needles
• Test all pregnant woman for HIV