Transcript Sexual reproduction in Human beings

Sexual reproduction in
Human beings
Learning outcomes
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Identify on diagrams of the male reproductive system
and give the functions of testes, scrotum, sperm
ducts, prostate gland, urethra and penis
Identify on diagrams of the female reproductive
system and give the functions of ovaries, oviducts,
uterus, cervix and vagina
Compare male and female gametes in terms of size,
numbers and mobility
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
Learning outcomes:
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Describe fertilisation and early development of
the zygote simply in terms of the formation of
ball of cells which becomes implanted in the
wall of uterus
Male reproductive organ
The male reproductive system
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Testes (testis)
Organ that produce the gametes and male sex
hormone (testosterone)
The testis constantly divide to produce up to
100,000,000 sperms per day.
The testis work more efficiently at just below
body temperature, so they are held outside the
body in scrotum.
The male reproductive system
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Storage duct/ epididymis
Sperms are stored in the storage duct
temporarily in an inactive form before it enters
the sperm duct.
The male reproductive system
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Sperm ducts/ Vas deferens
Tubes which carry the sperm away from the
testes
The male reproductive system
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Seminal vesicle/ Prostate gland
Is about the size of the golf ball
It adds a nutrient fluid and enzyme (seminal
fluid) in which it activates the sperms to swim
Sperms + seminal fluid = semen
The male reproductive system
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Urethra
The urethra is a tube that carries both urine and
semen along the penis to be released from the
body but at different times.
The male reproductive system
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Penis
It is an organ for introducing sperms into the
female. It contains spongy tissue which fills
with blood to make the penis firm (an
erection).
QUICK CHECK!
State the functions of:
Testes
Scrotum
Sperm ducts
Prostate gland
Urethra
penis
Female reproductive organs
The female reproductive system
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Ovaries
Female gonads
Making and releasing the female gametes
The female releases one ovum every four
weeks
The female reproductive system
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Oviducts/ Fallopian tube
Are tubes which carry the ova from the ovaries
They are lined with cilia together with a little
muscular assistance, help to move the ova
gently along.
The egg is fertilized in the oviduct.
The female reproductive system
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Uterus/ Womb
A pear shape organ
The wall contain involuntary muscle
The embryo develops in the uterus during
pregnancy
The female reproductive system
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Cervix
Cervix is the “neck” of the uterus, where the
uterus joins the vagina.
The female reproductive system
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Vagina
it is part of the female system which receives
the penis during the sexual intercourse
It is muscular and stretchable
QUICK CHECK!
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State the functions of:
Ovaries
Oviducts
Uterus
Cervix
vagina
Checkpoint 1:
Name the organ/ organs that carry out the function:
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Store matured sperms
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Carries both sperm and urine
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Produces cells with only half the number of
chromosome
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Produces the male sex hormone
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Receive sperm
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Egg must be fertilised here for pregnancy to
take place.
Female gametes vs male gametes
Female gametes vs male gametes
Female gametes
 Released one per month
 Unable to move by their
own
 Comparatively large
(o.1mm in diameter)
 A lot of cytoplasm which
contains nourishment for the
zygote if the ovum is
fertilised
 Nucleus always contains an
X chromosome
Male gametes
 Released in millions
 Able to move
 Very small (0.05 mm)
 Very little cytoplasm
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Nucleus contains either an
X or a Y chromosome
QUICK CHECK!
Compare the human male and female
gametes in terms of
(i)size,
(ii)numbers and
(iii)Movement
In each case, suggest reasons for the
differences you describe.
Human reproductive
system
Menstrual cycle
Menstrual cycle
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The average menstrual cycle is about 28 days.
Begins with puberty, ends with menopause.
Menstrual cycle is the alternation of
menstruation and ovulation.
Menstrual cycle
Menstruation:
 The spongy lining then peel away , damaging the blood
capillaries. The lining is passes out of the vagina, together with
the blood. Menstrual period. It lasts for about 5 days
Repair of uterine lining:
 Over a period of 14 days, the walls of the female’s uterus
develop a spongy lining
Ovulation:
 On day 14th, ovulation occurs. The ovum passes down the
oviduct. If the ovum is not fertilised by sperm, it passes
through the uterus and vagina and out of the vulva.
Thickening of the lining
 Lining continues to thicken for the next 10 – 12 days before it
begins to break down.
Menstrual cycle
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The fertile period is from day 11 to day 17,
because ovulation has occurred. Ovum can
survive for 2-3 days and allowing for the
possible survival of sperms in the oviduct.
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The rest of the time is considered infertile
period.
Factors affecting menstrual cycle
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Stress
Unbalanced diet/ malnutrition
Mental fatigue
Illness
These factors can alter or stop the menstrual
cycle
Menstrual cycle
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There are many developing follicles in the
ovary.
The young follicles are called primary follicles
A primary follicles are matured into a mature
follicle called Graafian follicle.
The mature follicle releases hormone
oestrogen that brings about the repair and
growth of the uterine lining.
During the ovulation, the one egg is released.
Summary
Menstrual cycle
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The ovary secretes progesterone after
ovulation.
Progesterone causes the uterine lining to
remain thick and soft and to become well
supplied with blood vessels. This is important
for preparation of the implantation of embryo.
Menstrual cycle
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If no fertilisation occur, progesterone
continues to be secreted for about ten days.
Then stop producing progesterone and this will
cause the onset of menstruation.
Reproduction
Fertilization and development of
embryo
Fertilization
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The egg released is surrounded by a few layers
of follicle cells.
As the sperm swim toward the egg, it will
release enzymes that digest the follicle cells.
Only one sperm enters the egg.
The fusion of the nuclei to form the zygote is
called fertilization.
The fertilization occurs in oviduct.
Development of embryo
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The zygote passes along
the oviduct to the uterus
and it begins to divide
by mitosis to form a ball
of cells that called
embryo.
The embryo becomes
embedded in the uterine
lining. This is called
implantation.
Development of embryo
Finger –like projections (villi) to provide large surface area for
diffusion
Allow dissolved food substances (glucose, amino acid, mineral
salts) and oxygen to diffuse from mother blood to the embryo
Allow metabolic waste (urea and carbon dioxide) to diffuse
from embryo to mother’s blood
Allow the antibodies to diffuse to the embryo
Produce progesterone
placenta
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umbilical
cord
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amniotic
fluid
Provide the buoyancy to the foetus, thus protect it from shock
and mechanical injuries
Maintains a relatively constant environment for the foetus.
Contain umbilical vein and two umbilical arteries
 bring dissolved oxygen and nutrients by the umbilical vein to
the foetus removing waste via umbilical arteries.
Development of embryo
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The exchange of the material between the foetus and
the placenta.
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Development of embryo
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Development of embryo
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The time between conception and birth is nine
months.
The nine months is known as the gestation
period.
At the end of the gestation period, contraction
of the uterus walls causes the rupture of the
amniotic sac.
The birth of the baby is followed by the
ejection of the placenta.
Thinking room?
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How are identical twins come about? Why do
they always - look alike and same sex?
IVF
A woman with blocked oviducts cannot have a baby in the normal way but can
now have a ‘test-tube’ baby. A doctor, using a fine tube through the
body wall, sucks up several eggs from the ovary, puts them in a dish and
mixes them with sperm. The eggs are then kept for a few days before
they are put back into the woman’s uterus via the cervix.
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Describe what can normally happen in the oviduct.
Why does the doctor get the eggs from the ovary through the body wall
and not through the vagina and uterus?
Why must the sperms be mixed with eggs before they are put back in the
woman?
Why do you think the eggs are kept for a few days before they are put
back into the uterus?
Why is the term ‘test-tube baby’ inaccurate?