2. Fetal Growth:
Conception to
Birth
We are all curious how
big the developing
baby is, what the baby
looks like as it grows
inside the womb and
when it moves how it
feels ? So lets Take a
peek inside the womb
to see how a fetus
develops from month
to month.
3. For the human species to continue surviving, it is
essential that mature adults are capable of producing
fertile offspring, to continue the existence of the species
and pass on genetic information from generation to
generation.This is done via reproduction.
The following is a step by step basis of how
reproduction occurs from beginning to end.
Gametes:
Before the initial cell can develop into a mature adult,
the building blocks to create that cell must be available
before fertilization can occur. Cells called gametes are
produced by mature adults via meiosis which contain
half the genetic information needed to produce the final
cell capable of growth.
4. Human males produce sperm, a gamete produced in the
testes
Human females produce ova, a gamete produced in the
ovarian follicles
For a short time period every month, the female gamete is
readily available to be fertilized by sperm, to form a zygote
They contain only one set of chromosomes and are said to be
haploid.
The male gamete, called the spermatozoa, is relatively motile
and usually has a flagellum. The female gamete, called the
ovum, is nonmotile and relatively large in comparison to the
male gamete. When the haploid male and female gametes
unite in a process called fertilization, they form what is
called a zygote. The zygote is diploid, meaning that it
contains two sets of chromosomes.
5. Chromosomes and Sex:
Chromosomes are long, stringy
aggregates of genes that carry heredity
information. They are composed of
DNA and proteins and are located
within the nucleus of our cells.
Chromosomes determine everything
from hair color and eye color to sex.
Whether you are a male or female
depends on the presence or absence of
certain chromosomes.
Human cells contain 23 pairs of
chromosomes for a total of 46. There
are 22 pairs of autosomes and one pair
of sex chromosomes. The sex
chromosomes are the X chromosome
and the Y chromosome.
6. Sex Chromosomes X-Y:
The male gametes or sperm cells in humans and other
mammals are heterogametic and contain one of two
types of sex chromosomes. They are either X or Y. The
female gametes or eggs however, contain only the X sex
chromosome and are homogametic. The sperm cell
determines the sex of an individual in this case. If a
sperm cell containing an X chromosome fertilizes an
egg, the resulting zygote will be XX or female. If the
sperm cell contains a Y chromosome, then the resulting
zygote will be XY or male.
Before a dividing cell enters meiosis, it undergoes a
period of growth called interphase.
7. Conception
The gametes, both
containing half the genetic
information needed to
produce the offspring, fuse
together, meaning all the
genetic information required
for the offspring to grow is
present. For this to occur,
sexual intercourse must
occur in order for the semen
(sperm) to be ejaculated
and have the potential to fuse with the ovum. At the moment
when a lone sperm penetrates a mature egg, conception or
fertilization takes place.
8. Ovulation
Each month, a mature egg
is released from one of a
woman's two ovaries -- this
is called ovulation.
Ovulation takes place about
two weeks after the first day
of the last menstrual period.
Millions of sperm are
released at the point of
ejaculation, and when
ejected, they 'swim' towards
the female egg with their
thread-like tail.
9. An average ejaculate
discharges 40-150 million
sperm which eagerly swim
upstream toward the fallopian
tubes on their mission to
fertilize an egg. Fast-swimming
sperm can reach the egg in a
half an hour, while others may
take days. The sperm can live
up to 48-72 hours. Only a few
hundred will even come close
to the egg, due to the many
natural barriers and hurdles
that exist in the female
reproductive tract
10. The Cells Begin to Divide
The fertilized egg begins dividing rapidly, growing into
many cells. It leaves the fallopian tube and enters the
uterus three to four days after fertilization. Rarely, the
fertilized egg does not leave the fallopian tube; this is called
a tubal pregnancy or ectopic pregnancy and is a danger to
the mother.
12. A. Identical Twins Fetuses are
of the same sex and share one
placenta. One outer
membrane envelops both
amniotic sacs. In some cases,
the zygote may proceed to an
external division and split up
into two separate cells. These
two new cells then continue
their development
independently
as they undergo their own segmentation. Eventually, they both
arrive in the uterus where they also implant separately. The result
is a twin pregnancy. Since both came from the same egg and the
same sperm, the twins will be identical, i.e., they will be of the
same sex and, of course, also look alike in every other respect.
13. B. Fraternal Twins Fetuses may
be of different sex. There are two
placentas and two separate
amniotic sacs, each with its own
membrane.
There are also some very rare
cases of multiple ovulation, i.e.,
the release of several eggs at the
same time. If these eggs are then
fertilized, they may, of course,
produce multiple pregnancies.
Twins born as a result of such a pregnancy are known as
fraternal twins. If three of these children are born, they are
called triplets, four are quadruplets, five are quintuplets, and so
on. Since each of them comes from a different egg fertilized by a
different sperm cell, they may be of different sex and will not
resemble each other any more than other brothers and sisters.
14. Implantation
Within hours of
conception the fused
gametes, a zygote,
undergoes cell division.
The presence of a
hormone called
progesterone prevents
further female eggs
being produced.
Within the first week after conception the fertilized egg
travels towards the uterus, where the continued growth of
the zygote will occur in the form of an embryo. Upon
arrival in the uterus, the zygote fuses itself to the uterine
wall.
15. At this point, cells of
the zygote
differentiate into two
distinct types
•Embryoblast Cells -
These cells
continually divide
into what will
become the embryo,
the baby itself
•Trophoblast Cells -
These cells form the
placenta, that form
against the uterine
wall
16. Pregnancy Hormones
Human chorionic
gonadotropin (hCG) is a
hormone present in the
blood within about a week
of conception. It is the
hormone detected in a blood
or urine pregnancy test, but
it usually takes three to four
weeks for levels of hCG to
be high enough to be
detected by pregnancy tests.
It is secreted by cells that
develop into the placenta.
17. The Placenta
After implantation, some
cells become the placenta
while others become the
embryo. The placenta is the
life support machine of the
developing embryo,
providing oxygen and food
for it and removing toxic
material and CO2 from the
developing embryo. The
umbilical cord, a connection
to the mothers' blood stream
is responsible for this.
18. The Embryo
By the end of the third week this
placenta provides a rich source
of nutrients for the unborn baby
that now is roughly the size of
this letter Towards the end of the
first month, the heart starts to
form while designated cells begin
to form the basic structure of the
limbs, spine, nervous and
circulatory systems. After the
initial formation of these major
bodily areas, less essential
characteristics begin to develop
such as the eyes, ears and nose.
19. Fetal development
at 4 weeks
At this point of
development the
structures that
eventually form the face
and neck are becoming
evident. The heart and
blood vessels continue
to develop. And the
lungs, stomach, and
liver start to develop. A
home pregnancy test is
now positive.
20. Fetal development
at 8 weeks
The baby is now about
the size of a grape -
almost an inch in size.
Eyelids and ears are
forming and even the
tip of the nose is visible.
The arms and legs are
well formed. The
fingers and toes grow
longer and more
distinct.
21. Fetal development
at 12 weeks
The fetus measures about
2 inches and starts to
make its own movements.
You may start to feel the
top of your uterus above
the pubic bone. Your
doctor may hear the
baby's heartbeat with
special instruments. The
sex organs of the baby
should start to become
clear.
22. Fetal
development at
16 weeks
The fetus now measures
about 4.3 to 4.6 inches and
weighs about 2.8 ounces. The
top of your uterus should be
felt about three inches below
your belly button. The baby's
eyes can blink and the heart
and blood vessels are fully
formed. The baby's fingers
and toes should have
fingerprints.
23. Fetal development at 20 weeks
The baby weighs about 9 ounces and is about six inches long.
The uterus should be at the level of the belly button. The baby
can suck a thumb, yawn, stretch, and make faces. Soon -- if
you haven't already -- you'll feel your baby move, which is
called "quickening."
24. Time for an Ultrasound
An ultrasound is generally
performed for all pregnant
women at 20 weeks of gestation.
During this ultrasound, the
doctor will confirm that the
placenta is healthy and attached
normally and that your baby is
growing properly in the uterus.
The baby's heartbeat and
movement of its body, arms, and
legs can also be seen on the
ultrasound. The gender of the
baby can usually be determined
at 20 weeks.
25. Fetal
development at
24 weeks
The fetus weighs about 1.4
pounds now. It responds to
sounds by moving or
increasing its pulse. You may
notice jerking motions if it
hiccups. With the inner ear
fully developed, it may be
able to sense being upside
down in the womb.
26. Fetal development
at 28 weeks
The fetus weighs about 2 pounds
6 ounces. It changes position
frequently at this point in
pregnancy. There's a good
chance of survival if your baby
was born prematurely now. Ask
your doctor about preterm labor
warning signs. Register for
birthing classes. Birthing classes
prepare you for many aspects of
childbirth, including labor and
delivery and parenting the
newborn.
27. Fetal development at 32
weeks
Often on the move, the fetus weighs
almost 4 pounds. The baby's skin
has less wrinkles as a layer of fat
starts to form under the skin. It will
gain up to half its birth weight
between now and delivery. Ask your
doctor how to do a fetal movement
chart. Think about breastfeeding.
Soon you may start leaking
colostrums from your breasts, a
yellowish fluid that precedes milk
production. Visits to the doctor
generally occur every two weeks at
this stage of pregnancy.
28. Babies differ in size, depending
on many factors (such as gender,
the number of babies being
carried, and size of the parents),
so your baby's overall rate of
growth is as important as the
actual size. On average, it's
about 12.5 inches and weighs 5.5
pounds. The brain has been
developing rapidly. Lungs are
nearly fully developed. The head
is usuallypositioned down into
the pelvis by now. A pregnancy is
considered 'at term' once 37
weeks has been completed; baby
is ready!
Fetal development at 36 weeks
29. Birth!
A mother's due date marks the
end of her 40th week. A
pregnancy begins with
implantation and the delivery
date can be calculated using the
first day of the last period.
Based on this, pregnancy can
last between 38 and 42 weeks
with a 'full term' delivery
occurring around 40 weeks.
Some post-term pregnancies -
those lasting more than 42
weeks - are not truly post-term.
A common "cause" is an
incorrect due date.
30. The Long Process of Child Birth,
Three Main Stages Of Child
Birth
This first stage is the
longest stage of the delivery process
and last for a mothers first child
usually between 12-18 hrs and gets
shorter for her second and third
and so on. This is the stage when
the water breaks, the Contractions
begin, and dilate the cervix to about
10 cm (contractions-when the
muscle on the top of the Uterus
presses down on the Cervix and
causes it to open, they will
eventually get closer together and
last longer, this causes the baby to
move down the birth canal).
31. The end of stage one is called the Transition. It is the
most uncomfortable time for the mother and the cervix
is almost all the way dilated, it's when the labor
becomes chaotic and the mother feel sick and is very
angry.
2)PUSHING- This stage lasts about 1/2 to 2 hrs for a
first time mother and shorter for a mother of multiple
children. The contractions become more intense and
last about 1 min and occur about every min. The crown
of the babies head begins to show(Crowning). Stage 2
ends with the delivery of the baby
3)AFTERBIRTH- This is the stage where the placenta
is delivered from the Uterus. It lasts usually about one
hour and is not often talked about and the mothers
usually don't even remember it..