Реферат: Fetal Development Essay Research Paper FertilizationFetal development

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Fetal Development Essay, Research Paper
Fetal development starts with the process of
fertilization. It starts when the female ovulates producing
an egg. This egg then travels into the fallopian tube where
it waits to be fertilized. Once sperm enter the body they
must travel up the uterus until they make their way up to
the egg. Once at the egg the sperm try to get in. They
sperm wiggle their tails until they make it in. Once it
makes it in the egg will not any other sperm in. The sperm
that made it then drops its tail. After about twenty hours
inside the egg the sperm finds the nucleus of the egg and
fuses with it. Now the egg has all the genetic material
that it needs to make a new human being. It nows begins to
move down into the uterus. The egg is now called a
blastocyst. The time that this takes is often measured
after the last menstrual period(LMP). The time is also
measured in trimesters, three month intervals.
After about thirty hours the cell divides for the first
time. It is continuously moving towards the uterus where it
will call home for the next nine months. After about two
days it has divided to having about eight cells. After four
days it is in the uterus and has to “land” somewhere and
attach itself to the endometrium. The eighth day is when
implantation occurs. The fertilized egg then implants
itself on the endometrium, the uterine lining, and begins to
grow. The cell begins to grow and develop. By the 12th
day the blastocyst has approximately two thousand cells in
it. It has had time to attach itself to the endometrium and
these anchors are called protuberances.
After about three weeks the tiny little heart is
developed enough to start beating and has the ability to
pump blood. At this time the blastocysts becomes an embryo.
There are three layers that form the embryo. These layers
are called the germ or cell layers. The outer cell layer
will eventually become the backbone, the brain, and the
nerves. This layer also makes the skin, the hair, and
The middle layer is going to be the lower layer of
skin, the bones, and the muscles. Blood and lymph vessels
are also made from this layer. Blood cells and the heart
muscles make a “primitive bloodstream (Nilsson, 1990, p.
77).” The sex organs and the kidneys also come from this
The inner layer makes up the a simple intestinal tube
with a mucus membrane. From that tube the lungs and urinary
tract form. Everything from all the layers then come
together to form the organ system. Then the embryo can do a
test run with the system. This happens every day while the
At around four weeks from the LMP the embryo begins to
form a backbone. The bones are split in two, half on each
side. The nerves begin to form down the middle of the bone
pieces. The placenta is by now drawing nutrients from the
mother. The nutrients then go down the umbilical cord into
the embryo. The wastes then go into the mother where they
After about five weeks from the LMP the embryo is
visible to the world outside. The doctors can look at the
embryo and measure it. The length is called the crown-rump
length. The sixth week is when the measurements are
Everything is continually growing and the whole body
straightens up. The head makes up about one-third of the
embryo’s body. There is still no skull so you can see the
brain. The arms as well as the legs are very short. This
is because the embryo grows from the head down to the toes.
That means the head is going to be huge compared to the rest
After six weeks from the LMP the embryo’s backbone has
come together and there are two arteries that run down each
side of it. The skin on the embryo is very thin and
translucent. The placenta and the embryo are connected by
the umbilical cord. The one large artery and two smaller
veins run through the umbilical cord. Everything that the
embryo needs will come through the umbilical cord.
After about eight weeks from the LMP the tiny little
embryo has every organ that it needs. The embryo is now
referred to as a fetus. The risks of miscarriages and
malformations has greatly been reduced. The brain is
visible from the outside of the fetus. It still isn’t
controlling the fetus because it has not been fully
By the third month the organ and organ systems are
becoming interconnected. The brain is starting to take over
the functions of the organs. The yolk sac is forming the
At the fourth month the fetus is over ten centimeters
long. It only weighs about twenty grams though. The face
is starting to form and look more human. The five
outgrowths that make up the face are moving into position.
One of them make up the nostrils and nose and the middle of
the upper lip. Two of the other outgrowths come from up
under each eye and form the cheeks and the rest of the upper
lip. The other two formed the lower lip and the chin.
The eye forms when the forebrain issues a hollow stalk
on both sides of the brain. The stalks start to thicken on
the end and this becomes the eyeball. The iris grows from
the edges in. Then the skin grows over the eye and this
The ear grows from three different parts. From the
skin a hollow area forms and this will be the inner ear. A
little after that the outer ear develops and the middle ear
then forms. Around the end of the fourth month the fetus
can hear sounds that come from the mother and the outside
The arm and the foot are formed by from little buds
that stick out from the body. These little buds keep
growing to form the arms and legs. At the end of the buds
there are little flipper like formations that will be the
hands and feet. The arms will get longer before the legs
will. After about the third month the hands can grab things
and the feet can kick. The kicks are usually to small for
The bones form from cartilage which is what is
initially formed in the fetus while it is still in the
uterus. The skull bones are flexible and they can be
damaged during labor. Sometimes collarbones and arm bones
can be broken and this really doesn’t cause much concern
because they just heal themselves. The bones usually heal
without scars or any traces of breakage.
During the third month after the LMP little hairs
appear on the fetus. “The fetus’s body starts growing a
fine hair called lanugo (from the Latin lana for fine
During the first few months of development you cannot
tell apart the male from the female by looking at them. A
small bud forms between the legs which will form the male
penis or the female clitoris. A swelling forms on either
side of the bump which will be the scrotum in boys. In
girls a slit will form and this will become the vagina. The
testicles form deep inside the abdomen. The male can
produce sperm right up to an old age. The ovaries already
have all the eggs that the women will ever need in her life.
Approximately half way through the pregnancy the mother
can start to feel the fetus kicking inside of her. Then
after a couple more weeks the fetus has grown to little over
a pound. The fetus can see some light as it comes through
the abdominal wall. “The fetus may frequently suck its
thumb” (Silverstein, Silverstein, and Silverstein, 1994,
During the seventh month after the LMP the fetus starts
to put on weight. The weight of the fetus increases by
nearly half a pound a week. the mother has to watch her
weight because overeating during pregnancy can be bad for
the fetus. If the mother doesn’t eat enough the fetus can
be starving for food and that can impact the brain of the
fetus and cause malformations. Smoking or drinking during
pregnancy can form defects in the fetus and cause it to be
The fetus is growing in size and has been training for
his entrance into the real world. He has been moving around
for quite awhile, since about the eighth week. When the
fetus moves inside the uterus he is not just playing he is
helping to build muscle and strengthen his bones at the same
time. At this time the fetus is also starting to run out of
room in the uterus. Now the fetus can’t do somersaults
like it used to earlier in development. Sometimes the fetus
can get hiccups, the mother feels these as small jerks.
During the eighth month after the LMP the fetus has
double his weight and now weighs about five and a half
pounds. The brain and central nervous system has developed
far enough that if the fetus was to be born now he would
have a good chance of surviving. The fetus is often checked
by a doctor to see if he is in the right position, head
The ninth month after the LMP is when the fetus puts on
a lot of weight. “The majority of fetal weight gain occurs
in the third trimester”(Goliers Encyclopedia
Inc.,1997,CD-ROM). Most of the lanugo has disappeared by
now and is swallowed by the fetus. This collects at the
bottom of the bowel. It forms a greenish-black ooze called
meconium. The baby will pass this through as his first
During the first trimester the mother can and will
experience vomiting and nausea, also called morning
sickness. These symptoms usually occur after about eight
weeks after the LMP. The mother will experience increased
urination due to the pressure on the bladder. “Breast
soreness or tingling often occurs do to the hormonal
stimulation”(Software Toolworks Multimedia
Encyclopedia,1992,CD-ROM). Fatigue is also common.
During the second trimester the mother will most likely
experience constipation. Sometimes the uterus will contract
may occur. They are called Braxton-Hicks contractions. She
may also feel lightheaded and faint. This is caused by the
diversion of blood to the uterus, placenta, and fetus. The
mother may also experience heartburn because the fetus is
growing in size which causes pressure to be placed on the
stomach. This stage is more comfortable than the first.
The third trimester become more uncomfortable than the
first two. The mother may get hemorrhoids, headaches,
swelling of the legs, and varicose veins may occur. The
lungs cannot take in enough oxygen so the mother may feel
short of breath. Near the end of the fetal developmental
stage she may experience pelvic discomfort because the fetus
is settling into the position that he will be born by, head
down near the pelvis. Insomnia may also be an occurrence
days prior to the delivery. The mother may feel false labor
There are three signs that can warn the mother that
labor is beginning, there are regular contractions, the
membrane ruptures (”water breaking”), and mucus mixed with
blood. During the last month of pregnancy there are usually
contractions that don’t mean much. When the contractions
are less then about ten minutes apart then that is a sure
sign that labor has begun. Sometimes labor will begin with
the amniotic fluid flowing out of the vagina. This means
the amniotic sac around the fetus has ruptured and the
mother should get to the hospital immediately. “The uterus
was contracting, or squeezing, to push you out into the
Once the mother is at the hospital she will find it a
nice place to be. The hospital equipment has changed over
the years and the mother should be quite comfortable. Most
of the time the mother will have someone with her, such as a
Labor most likely happens in three stages. First the
dilatation stage begins. This starts when the contractions
begin or the water breaks. During this stage the cervix, or
the opening at the bottom of the uterus, is expanding and
opening to a larger size. When the cervix is fully dilated
it is about four inches across. While all this is happening
the fetus’s head is settling into the birthing position.
This stage of labor is the longest and can take anywhere
from six to twenty hours. If the mother has given birth
The second stage of labor is called the expulsion
stage. This stage lasts from the time that the cervix is
fully dilated until the baby is born. This is the stage
where the mother has to push the fetus out of the uterus.
This stage of labor normally takes from just about a few
The last stage of the delivery is called the delivery
of the placenta. It begins right after the baby is born
until the entire placenta is expelled from the uterus. This
stage normally takes about fifteen minutes to complete. But
it could take up to an hour. This stage is usually the
The fetus has a lot of stress being put on him when he
is being born. During the contractions the fetus has a
small lack of oxygen due too the pressure being put on the
placenta and the umbilical cord. During the contractions
the fetus’s heartrate slows down but regains its strength in
between the contractions. This phase of labor is very
punishing on the fetus and the adrenal glands start
producing massive amounts of adrenaline and noradrenaline.
The adrenaline is important because it helps to keep the
heart going if the oxygen supply is cut off. It keeps the
blood flowing to the sensitive brain and raises blood-sugar
levels. The adrenaline also helps to clear the lungs of the
liquid that has been in their since the beginning of the
fetus’s life. It also helps to prepare the lung for
breathing in the outside air. Once out of the mother the
babies umbilical cord is cut and the baby is on his own.
The mother may experience great pain during this phase
of the pregnancy. To help her relax the husband will
usually give her a massage. Just having the father there
will make the mother be more comfortable. If she feels the
need for pain relievers there are several kinds. She could
be given pethidine but that would affect the baby. Another
option is inhaling a mixture of nitrous oxide and oxygen.
She could also be given a local anesthetic to the nerves of
the cervix to relieve the pain. But the most common type of
pain relief is the epidural anesthetic. It numbs the nerves
right as the come out of the spinal cord.
After the baby is born he is checked by a nurse,
measured, and weighed. Then he is wrapped in a blanket and
given to the mother. The baby is then moves towards the
mother’s breast by instinct. This helps to teach the baby
how to suck. The baby will feed up to ten times a day. The
mother’s breasts may become swollen and tender due to the
production of milk. The mother’s milk is loaded with
nutrients and minerals that is essential to the development
of the baby. It is recommended that the child be
breast-feed for at least 3 months and if at all possible
Cole, J. (1984). How You Were Born. New York: William
Goliers Encyclopedia (CD-ROM). (1997). Fetal
Multimedia Encyclopedia (CD-ROM). (1992). Fetal
Nilsson, L. (1990). How You Were Born. New York: Delacorte
Silverstein, A., Silverstein, V., Silverstein, R.
(1994). The Reproductive System. New York: Twenty- First
Vaughan, C. (1996). How Life Begins. United States: Times

Название: Fetal Development Essay Research Paper FertilizationFetal development
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Реферат: Fetal Development Essay Research Paper FertilizationFetal development
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