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Fetal Development Essay, Research Paper

Fertilization

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

layer.

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

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