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Embryonic development begins
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Blood islands form in the umbilical cord
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The erythroblasts in the yolk sac form
Three different types of blood forming cells form in the yolk sac -
More blood islands form in the umbilical vesicle
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Spleen primordia forms
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Thymic primordia forms
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Thymus forms
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The blood begins to form in the liver
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The greater thymic bud forms
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The bone marrow replaces the cartilage in the humerus
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The langerhans cells enter the epidermis
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The palatine tonsils form
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Birth
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http://php.med.unsw.edu.au/embryology/index.php?title=Timeline_human_development
http://www.foxnews.com/health/2013/04/09/babies-immune-system-development-influenced-by-birth-month/
http://www.sciencedaily.com/releases/2013/04/130408184634.htm
http://www.whattoexpect.com/pregnancy/your-baby/week-33/water-weight.aspx
