PRENATAL DEVELOPMENT

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PRENATAL DEVELOPMENT
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Prenatal Development
Life begins in the reproductive system of the
female, set inside the pelvic cavity.
The term natal means birth so pre-natal
means before birth.
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Endometrium (uterine wall)
Fallopian Tube
Ovum is ripening inside follicle
Ampulla
.
Fimbria
Maturing follicles
Ovary
Cervix a mucous plug forms in this area during
pregnancy
Uterus (womb)
Vagina
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Egg maturation and ovulation is stimulated by two
hormones secreted by the pituitary gland-
follicle stimulating hormone (FSH) and
luteinizing hormone (LH). Approximately every 28
days, at the start of a cycle, these hormones
cause several follicles to start growing. Of
these, only one matures to form a large
fluid-filled structure that contains a ripening
egg. When the egg matures it is released from the
follicle when the follicle rupturesin a process
called ovulation. This occurs on about the 14th
day of the cycle. The egg contains 23
chromosomesthe mothers genetic material.
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The egg, or ovum, slowly travels through the
fallopian tube, and if sperm are present at that
location, one may unite with the ovum in a
process called fertilization. Only one sperm can
enter the eggs outer membrane. The moment the
sperm penetrates the egg is called conception,
creating a new and separate cell called the
Zygote. The penetrating sperm loses its tail,
the head dissolves, and out spills its genetic
material23 chromosomes.
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CELL DIVISION
The fertilized egg now has 23 PAIR, or 46
chromosomes. Immediately the cell begins to
duplicate, taking approximately 30 hours to
complete the first cell division.
At an increasingly faster rate, new cells are
added until they form a hollow, fluid-filled
ball, called a blastocyst (about 4 or five days
after conception). Approximately 60 to 70 cells
form the blastocyst. Those on the inside (called
the embryonic disk) will become the new organism
whereas those on the outside will provide the
protective covering.
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Multiple births can occur two different ways.
Sometimes two (or more) different eggs are
released, and both are fertilized by two
different sperm. The result is fraternal twins.
They may be both boys or both girls or one of
each they may or may not look similar. In other
cases, a single egg fertilized by a single sperm
will split completely in half during that very
first cell division. This results in identical
twins. They will both be of the same sex and will
look very similar if not the same. Identical
twins have identical DNA, but different
fingerprints!
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All the time an egg has been ripening and
preparing for ovulation, the endometrium of the
uterus has been forming a nutrient-rich lining.
It is preparing to receive a fertilized egg. (If
no egg is fertilized, this lining will leave the
body during a process called menstruation.)
Around the seventh or ninth day after conception,
the blaystocyst burrows into the uterine lining
in a process called implantation. The protective
covering quickly develops into the amnion,
surrounding the organism in amniotic fluid. A
yolk sac also develops, producing blood cells
until the liver, spleen, and bone marrow is
mature. The womans ovaries produce massive
doses of the hormone progesterone, signaling the
body that a pregnancy is in progress.
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Nerve growth begins when a sheet of cells on the
back of the embryo folds in the middle to form a
tube, which will become the future spinal cord.
At one end tube enlarges to form the brain's
major sections. The amniotic fluid that cushions
the fetus begins to form.
Week 4
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5 weeks -  At this time the embryo is still the
size of a raisin. Low on the sides of the head
are two folds of tissue that will become the
ears. Although not completely developed, all the
major body organs and systems are formed. The
neural tube enlarges into three parts, that will
soon to develop to become a very complex brain.
Also the placenta begins functioning, including
the chorionic villi and the umbilical cord,
through which the baby will receive nourishment
and oxygen. The spine and spinal cord grows
faster than the rest of the body at this stage
and will give the appearance of a tail. This
disappears as the baby grows.
                          
WEEKS 5 6
The tail in this tadpole stage is found in
many organisms, so was used as evidence in
Darwins theory of evolution.
6 weeks - The embryo's tiny heart begins to beat.
The embryo itself is about a 1/4 inch long. Other
major organs, including the kidneys and liver,
have begun to develop, and the neural tube, which
connects the brain and spinal cord, closes. The
physical sensations of pregnancy start--nausea,
fatigue, sore breasts and frequent urination.
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• There are two patterns of development occurring
  throughout development of the being
• Cephalo-caudal, meaning head to tail, top to
  bottom
• Proximal-distal, meaning inward to outward

(the head before the heart the internal organs
before the limbs)
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WEEK 7
7 weeks - The embryo's hands and feet are shaped
like paddles, but the fingers are beginning to
take shape. The embryonic tail has almost
disappeared. The pituitary gland is also forming
and the fetus is beginning to grow muscle fibers.
The heart has divided into the right and left
chambers and is beating about 150 beats a minute
which is about twice the rate of an adult. The
baby's facial features are visible, including a
mouth and tongue. The eyes have a retina and
lens. The major muscle system is developed, and
the baby starts to practice moving. The baby has
its own blood type and the blood cells are
produced by the liver now instead of the yolk sac.
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8 weeks- The unborn baby is now called a fetus.
The fetus is protected by the amniotic sac and
filled with fluid. Inside the child swims and
moves gracefully. The fetus is now about 3/4
inches long. The arms and legs have lengthened.
During this time of development, the baby's head
appears much larger than the body because the
brain is growing very rapidly. Brain waves can
now be measured. The teeth and the palate are
beginning to form and the larynx is developing.
Through its parchment-thin skin, the baby's veins
are clearly visible. By the eighth week the ears
begin to take shape. 9 weeks - Though the fetus
is constantly moving, you won't be able to
actually feel fetal movement for several more
weeks. All of the organs, muscles, and nerves are
in place and beginning to function. As the hands
and feet develop fingers and toes, they lose
their paddle-like look, and the touch pads on the
fingers form.
WEEKS 8 9
THE FETUS
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WEEKS 10-11
10 weeks - The fetus weighs about 1/3 of an
ounce. The heart is almost completely developed
and very much resembles that of a newborn baby.
The eyelids have fused shut. The wrists and
ankles have formed and the fingers and toes are
clearly visible. Genitals have begun to form, but
it is too early to tell the sex of the fetus.  
11 weeks - The vital organs--the liver, kidneys,
intestines, brain and lungs--are fully formed and
may begin to function, while the the head is
almost half the length of the entire body. The
fetus is only about 2 inches long and weighs less
than a half ounce but it is busy moving and
kicking. 
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Vocal chords are complete, and the baby can and
does sometimes cry silently. The brain is fully
formed, and the baby can also feel pain. The
fetus may even  suck his thumb. The eyelids now
cover the eyes, and will remain shut until the
seventh month to protect the delicate optical
nerve fibers. The hair is on the head and the
fingers and toes have developed soft nails. The
kidneys are developed and begin to secrete urine.
The skull is not solid bone, but has formed in
sections. These sections can overlap during the
birth process. There are even a couple of soft
spots where bone has not formed at all called
fontenals.
WEEK 12
During this first trimester period of
formation, many things can go wrong. Sometimes
the womans body will self-abort. This is called
a miscarriage.
THIS IS THE END OF THE FIRST TRIMESTER, WHEN THE
MAIN TASK WAS FORMATION!
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Umbilical cord
A CLOSER LOOK
INTO THE WOMB...
Placenta

Amniotic sac filled with amniotic fluid
Mucous Plug
Caution!... besides oxygen and nutrients, the
cord delivers nicotine, alcohol, drug compounds,
and other things ingested, inhaled, or absorbed
through the skin of the mother.
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DON'T FORGET THE MOTHER'S HEALTH...
Nutrition is extremely important during
pregnancy. Eating a well-balanced diet can
prevent birth defects in the fetus, low-birth
weight/mortality of the infant, a difficult
labor/delivery, and mortality of the mother
during childbirth. The fetus is creating new
bones, blood cells, tissue, etc. If it does not
receive the nutrients it needs through mothers
dietit will get it by taking it out of mothers
own system, i.e. robbing calcium from the
mothers bones to build its own bones. If
deficiencies exist, problems may show up right
away or years later.
Common health problems developing during
pregnancy Preeclampsia and Eclampsia (high blood
pressure)Gestational DiabetesInfections
(toxemia)Clotting Disorders Common disorders of
pregnancy Placental ProblemsPreterm
LaborPreterm Premature Rupture of the
MembranesFetal complications Congenital
AbnormalitiesGrowth Abnormalities
Remember exercise and the emotional health of the
mother as well!
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4TH MONTH
Weeks 13-16
By now, the fetus has grown large enough that the
movements can sometimes be felt by the mother.
Often felt like a flutter or a "flip-flop", these
first movements that can be felt by the mother is
called quickening.
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At the end of the fourth month, white, downy
hair called lanugo (lu- noo- go) covers the
entire body of the fetus. It provides warmth,
since the fetus has no layer of fat beneath the
skin yet.
At some point later, a white waxy, cheese-like
substance also forms over the entire surface of
the skin. This is called vernix caseosa. The
vernix is a perfect skin lotion, which along with
the lanugo, protects he skin from the constant
exposure to amniotic fluid. It is also believed
that it serves as a sort of skin cleanser and
antibacterial substance. The lanugo and vernix
caseosa diminishes in amount during the last
weeks of the gestation period and usually rubs
off during delivery. The presence of a great
deal of vernix or lanugo at the time of birth,
therefore, is often a sign of prematurity.
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The fetus also shows a sensitivity to light and
can be stimulated and irritated. However, it
still has a long way to go before it is mature
enough to survive outside of the womb. Although
there are a few cases of infants being born and
surviving at this time, the chance of survival
(and without later complications), is very slim.
During the 5th month, at 22 weeks, the fetus
weighs a little over 1 pound, and is about 1 foot
in length. At this time, the movements can
clearly be felt by the mother and by others who
place their hands over the mother's abdomen.
5TH MONTH
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During the 4th-6th months, most of the organs
that were formed during the first trimester begin
to function. If born at this time, the fetus has
a chance survival. The point in which it can
first survive is referred to as the age of being
viable and occurs sometime between 22 and 26
weeks.
MONTH
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THIS IS THE END OF THE SECOND TRIMESTER, WHEN THE
MAIN TASK WAS FUNCTIONING!
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At only about 3 pounds, the 7 month old fetus has
a few pounds to go before reaching the average
7.5 pounds. During this time, the brain
continues to develop at an increasingly fast
rate. By 7 months, the fetus clearly responds to
sounds outside of the womb, and develops a
preference for the tone and rhythm of its
mother's voice.
MONTHS
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By the eight month, the fetus has little room for
large movements. During this month, a layer of
fat is added that will assist with temperature
regulation. The lungs however, still remain
immature. If born at this time, the infant will
likely require some help with breathing. It is
not until the ninth month that the lungs are
mature enough to regulate breathing without
assistance.
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During this last month of the gestation period,
baby continues to grow at a rate of ½ to 1 pound
per week. Baby will turn around in the womb, to
a head-down position. The lungs are maturing,
preparing for that first breath.
9TH MONTH
THIS IS THE END OF THE THIRD TRIMESTER, WHEN THE
MAIN TASK WAS GROWTH!
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THE END
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• Preparing individuals for life and work
• Strengthening families
• Empowering communities
• Created by Barbara L. Swarthout, Family
  Consumer Sciences teacher at Elkhorn High School