Embryology is a branch of biology. It studies development of embryos. Embryos are formed after an egg cell is fertilized.
It takes 20 to 21 days for a chicken to hatch. Each day is full of events that happen inside the egg.This 20 to 21 day period is called incubation. Before the incubation period , fertilization occurs. In chicken, fertilization happens about 24 hours before a hen lays an egg. The cells starts dividing inside the egg. Once the egg is laid the division of cells stops.
DAY
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EVENT
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1
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The first day of chicken development is full of events. Many important parts begin to develop. For example, nervous system with beginning of brain and spine start to develop. Also, the head start to form. In the end of the first day blood starts to flow and eyes begin to form.
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2
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During the second day a tiny embryo continues to develop. Yolk of the egg starts to have blood vessels that feed the embryo. This also means that circulatory system is starting to form parts like heart and blood vessels. After 30 hours we can hear the heart beat. Ears and brain also are developing.
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3
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In the third day the embryo gets surrounded by amniotic fluid. This fluid is just like in human baby - it feeds and protects the embryo. The tiny embryo is also changing and wings and legs are beginning to grow.
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4 -5
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During the days four and five the development continues quickly. During these days gizzard and tongue are formed. We can also find out if the chicken is a girl or a boy because they start to develop reproductive system. One important event that happens during these two days is that the yolk of the egg and the embryo get totally separated.
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6-8
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One of the most important things that happens during these days is that the chicken embryo actually starts to control movement. This means that it can move feet or wings on purpose. During these days the beak and the feathers start to form, and embryo starts to look more like the chicken.
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9-12
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The embryo looks more and more like a real chicken, and first real feathers appear. The beak becomes hard. Embryo now has toes and skin.
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13-15
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The development continues and the body has more and more feathers. Also, claws, scales and beak continue to get harder. An important thing that happens during these days is that the small intestine develops.
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16-18
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By the 18th day, the development is almost complete. In the days 16-18 the embryo gets all of its feathers. The beak and claws become really hard. Also, the embryo fills almost the whole egg and starts to get ready to come out.
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19-20
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The egg is now filled with an embryo. The only space left in the egg is the air sac. By the day 20 the embryo becomes a chicken. This happens when it starts actually breathing the air in the air sac.
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21
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Today is the day!
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Would you like to learn more about the chicken embryology?
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