Реферат: Fetal Development Essay Research Paper FertilizationFetal development

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.

Embryonic Development

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

sebaceous and sweat glands.

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

organs are being formed.

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

are discarded.

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

normally taken.

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

of the body.

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.

Fetal Development

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

developed yet.

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

blood cells.

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

becomes the eyelid.

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 mother to fell them though.

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

bowel movement.

The Pregnant Body

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

pains which can be uncomfortable.


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

world (Cole,1984,p.30).

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

mother or her husband.

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

before the time will be less.

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

minutes to a little over an hour.

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

easiest of the three.

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 Birth

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

Morrow and Company, Inc.

Goliers Encyclopedia (CD-ROM). (1997). Fetal


Multimedia Encyclopedia (CD-ROM). (1992). Fetal


Nilsson, L. (1990). How You Were Born. New York: Delacorte

Press/Seymour Lawrence.

Silverstein, A., Silverstein, V., Silverstein, R.

(1994). The Reproductive System. New York: Twenty- First

Century Books.

Vaughan, C. (1996). How Life Begins. United States: Times


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