Fetal development
Fetal developmentFertilization
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...
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