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Fetal
Development
First
Trimester
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The unborn child
at seven weeks
(5 weeks after conception) |
Years
ago, while giving an anesthetic for a ruptured tubal pregnancy (at two
months) I was handed what I believed to be the smallest human being ever
seen. The embryo sac was intact and transparent. Within the sac was a tiny
human male, swimming extremely vigorously in the amnionic fluid, while
attached to the wall by the umbilical cord. The tiny human was perfectly
developed, with long, tapering fingers, feet and toes. It was almost
transparent as regards to the skin, and the delicate arteries and veins were
prominent to the ends of the fingers. The baby was extremely alive and did
not look at all like the photos and drawings of 'embryos' which I have seen.
When the sac was opened, the tiny human immediately lost its life and took
on what is accepted as the appearance of an embryo at this stage, blunt
extremities, etc.
Paul E. Rockwell, M.D.
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2
weeks
- Fertilization: the sperm and egg join in the fallopian tube to form a
unique human being. Forty-six chromosomes combine, which pre-determine all
of a person's physical characteristics.
The picture on the right
is a fertilized egg, only thirty hours after conception. Magnified here, it
is no larger than the head of a pin. Still rapidly dividing, the developing
embryo, called a zygote at this stage, floats down from the fallopian tube
and towards the uterus. |
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3 weeks
- Once in the uterus, the developing embryo, called a blastocyst, searches for a
nice place to implant, where it actually burrows beneath the surface of the
uterus. The yolk sac, shown on the left, produces blood cells during the early
weeks of life. The unborn child is only one-sixth of an inch long, but is
rapidly developing. The backbone, spinal column, and nervous system are forming.
The kidneys, liver, and intestines are taking shape.
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4
weeks - The embryo produces
hormones which stop the mother's menstrual cycle.
5 weeks
- Embryo is the size of a raisin. By day twenty-one, the embryo's tiny heart
has begun beating. The neural tube enlarges into three parts, soon to become
a very complex brain. The placenta begins functioning. The spine and spinal
cord grows faster than the rest of the body at this stage and give the
appearance of a tail. This disappears as the child continues to grow.
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7
weeks - Facial features are visible,
including a mouth and tongue. The eyes have a retina and lens. The major
muscle system is developed, and the unborn child practices moving. The child
has its own blood type, distinct from the mother's. These blood cells are
produced by the liver now instead of the yolk sac. |
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8
weeks - The unborn child, called a
fetus at this stage, is about half an inch long. The tiny person is
protected by the amnionic sac, filled with fluid. Inside, the child swims
and moves gracefully. The arms and legs have lengthened, and fingers can be
seen. The toes will develop in the next few days. Brain waves can be
measured. |
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10
weeks - The heart is almost
completely developed and very much resembles that of a newborn baby. An
opening the atrium of the heart and the presence of a bypass valve divert
much of the blood away from the lungs, as the child's blood is oxygenated
through the placenta. Twenty tiny baby teeth are forming in the gums.
12 weeks
- Vocal chords are complete, and the child can and does sometimes cry (silently).
The brain is fully formed, and the child can 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. |
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(see sources)
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