Mothers notice mild elbow and
knee jerks the irises dilate and contract in response to light. It also
urinates about half a litre a day.
So it
has to be a living baby swimming inside.
Fig.2 The baby starting an aerial life is merely a stage in
the development.
Male Sex Organs
The testes are the primary male sexual organs. They make the
sperms and produce testosterone. The sperm cell is the male sex cell (gamete).
Testosterone is the hormone that causes male secondary sex characteristics such
as facial and pubic hair, thickened vocal cords and developed muscles. The
testes are placed in a sac called scrotum outside the male body. . Each testis
is provided with tubules up to a length of about 250 meters. The sperms develop
inside these at a temperature of 35 to 36 C which is one or two degrees below
the body normal.
The rudimentary sperms travel from testis to a tube on the
outer surface of testis called the epididymis, where they mature in about 20
days. The sperms exit the body through the penis. The penis is made of soft,
spongy tissue. When filled with blood during sexual excitation, the spongy
tissue stiffens, to place the sperms inside the female. The sperm get mixed
with nutrient-rich fluids from the seminal vesicles and a milky secretion from
the prostate gland. This combination of sperm and fluids is called semen.
Functions of semen.
- Provides a watery
environment in which the sperm cells can swim while outside the body
- Provides nutrients
for the sperm cells (fructose, amino acids, vitamin C)
- Protects the sperm
cells by neutralizing acids in the female's sexual tract
Fig.3 Organs where the sperms are produced.
Fig.4 One from the millions of sperms ejaculated at a time.
Female Sex Organs
Sex organs of females are within the body except the vulva.
The vulva consists of two sets of folded skin (labia major, labia minor) that
cover the opening to the reproductive tract, and a small nub of sensitive,
tissue, clitoris, which is a vestige.
The two ovaries are the major female sex organs which are
inside the abdomen. They produce the eggs, which are the female gametes, and
produce estrogen, the female sex hormone. Estrogen causes female secondary
sexual characteristics such as pubic hair, breast development, widening of the
pelvis and deposition of body fat in hips and thighs.
Fig.4. Female reproductive organs.
Fertilization
With the combination of the pro-nuclei of the sperm and the
egg cell, the zygote will have 46 chromosomes. These are all the genetic
information the baby will ever receive.
For the rest of his
life, nothing new will be added except nourishment.
|
Day
|
Development
|
Diagrams
Fig 5. Only one sperm enters the egg.
|
|
1
|
Millions of sperms swim toward the
egg cell along the vagina. The heads of sperms may be guided by heat, smell
or electrical charges.
Less than 1000 out of millions
reach the oviduct.
|
|
2
|
The head of each sperm releases enzymes that begin to break down the outer,
jelly-like layer of the egg's membrane, trying to penetrate the egg. Once a
single sperm has penetrated, the cell membrane of the egg changes.
|
|
3
|
The pro-nucleus of the
sperm merges with the pro-nucleus of the egg cell.
This is
fertilization. The resulting cell is called a zygote.
Cell division begins immediately
|
Fig.6 Fertilization
|
|
4
|
Zygote gets pushed
along the oviduct (fallopian tube) by cilia.
|
Fig.
Eight-celled stage
|
|
7
|
Now it's called a blastocyst. When this reaches the
uterus, and gets attached by the sixth day after fertilization
About 100 cells that will form the placenta surround the cavity.
|
|
Weekly progress.................
|
Week
|
# Size
|
Development
|
|
2
|
256 cells1/100 of an inch
|
Tiny heart beating.
|
|
3
|
4-6 mm.
|
The foundation for the nervous system is laid
down.
|
|
4
|
8-11 mm
|
Blood circulation gets established
Limbs and internal organs begin to form.
|
Monthly progress.................
|
End
of a Month
The head and trunk
developed.
The limb buds appear.
Blood is beginning to be pumped.
Heart beat is visible by ultrasound.
Reflexes are present
The skeleton is complete.
Movements may be detected.
The baby has all the internal organs of an adult.
The process of ossification (the hardening of the bones) begins.
|
|
|
Placenta as a Barrier.
Placenta is a device which allows
the transference of gases and nutrients without letting the mothers blood get
into the embryo.
|
Substances that cannot pass through
|
Substances that can pass through
|
|
Blood cells
Bacteria
Nicotine
|
Gases
Nutrients
Nitrogenous waste
Some viruses
Alcohol
Drugs
|
|
|
|
Month
|
Size
|
|
|
|
2
|
3 to 5cm.
4 to 7
grams
|
Upper lip, external
ears, and external genitalia are visible.
|
|
|
Fingers and toes begin
to form.
Reflex activity begins
with the development of the brain and nervous system.
The iris of the eye
and the finger nails appear now.
He can squint,
swallow, move his tongue, and would make a fist if you were to stroke his
palm.
|
|
3
months
140 to 375 g.
|
The baby's brain now
has the same structure it will have at birth. all body systems begin
functioning
The baby's teeth have
formed. The baby is sucking his thumb.
Using ultrasound, the
baby's gender may be detected.
. Loud noises might startle him
|
|
4
months
1.5 kg.
25
cm
|
The foetus can respond
to sound
The chances of
survival get better and better with every passing day.
The baby urinates
about a half liter of urine everyday.
Mothers may notice
smaller movements such as those of the baby's elbow and knees.
|
|
|
5
months
|
The baby's irises
dilate and contract in response to light changes in the uterus.
The baby is now putting on about .5 pounds a week.
|
|
6
months
to
9
months
3 kg.
|
The head goes down..
Ready to be born.
The uterus makes
rhythmic contractions.
The cervix dilates.
The amnion (water bag)
breaks and the liquid goes out.
Muscular contractions
expel the child.
Uterus bleeds for a
few days.
Mother is liable to
infection.
|
|
|
The End
1.0 Match the
following parts and functions.
|
Part
|
Connect
|
Function
|
|
1. Testes:-
|
|
1. Two
sets of folded skin
|
|
2. Ovary
|
2. Fertilization.
|
|
3. Epididymus
|
3. Holds
the embryo to the uterus
|
|
4. Scrotum
|
4. A
sac holding the male sex organs.
|
|
5. Uterus
|
5. Supplies the pressure for semen to
eject.
|
|
6. Penis
|
6. Embryo
develops here
|
|
7. Prostate gland
|
7. Produces
sperms
|
|
8. Placenta
|
8. A
tube of about 6 meters
|
|
9. Fallopian tube.
|
9. Produces
ova (eggs)
|
|
10. Vulva.
|
10. Injects
the semen into the female
|
2.0
Give the difference between male and female sex cells (gametes) with regard to
the following counts. Fill in the blank
spaces in this table
Sex | Name of Cell | Where produced | Numbers produced at a time | Size | Mobility |
| Male | Sperm | b. | Millions | Head only 0.01mm | e |
| Female | a.. | Ovary | c. | d | Immobile. Pushed by cilia in the tube. |
| 3.0 Label the numbered parts in this diagram of the female reproductive system.. 1……………………………. 2…………………………… 3…………………………….. 4……………………………… 5………………………………… |
|
|
Part
|
1
|
2
|
3
|
4
|
5
|
6
|
|
8
|
9
|
10
|
|
Function
|
7
|
9
|
8
|
4
|
6
|
10
|
5
|
3
|
2
|
1
|
10
marks.
|
#
|
a
|
b
|
c
|
d
|
e
|
Marks
|
|
2.0
|
Egg. (ovum)
|
testes
|
one
|
0.05mm
|
Swims with a tail like flagella.
|
5
|
|
3.0
|
1.testes.
|
2.Oviduct
|
3. Funnel of uterus.
|
4.Uterus
|
5.Cervix
|
5
|
