-
Day 1
Embryonic development begins -
Week 1, 6 days
Blood islands form in the umbilical cord -
Week 2, 2 days
The erythroblasts in the yolk sac form
Three different types of blood forming cells form in the yolk sac -
Week 2, 6 days
More blood islands form in the umbilical vesicle -
4 Weeks
Spleen primordia forms -
Week 4
Thymic primordia forms -
4 Weeks, 4 days
Thymus forms -
6 Weeks
The blood begins to form in the liver -
6 Weeks, 5 Days
The greater thymic bud forms -
8 Weeks, 1 Day
The bone marrow replaces the cartilage in the humerus -
Week 10-12
The langerhans cells enter the epidermis -
10 Weeks
The palatine tonsils form -
40 Weeks
Birth -
Sources
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
