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Early embryonic development, with stages including implantation of the blastocyst and development of the supplying blood vasculature to the embryo. Day 7: arrival in the uterus and implantation. Day 7+: beginning trophoblast. Day 12: microvilli stage. Days 13 to 19: yolk sac stage and end of presomite stage. Days 23 to 28, embryo with head and tail apparent.
Transparent glass man and woman, showing the organs involved in sexual attraction, especially those that secrete sex hormones. The testes in the male and the ovaries in the female are highlighted, and in both the male and the female, the brain is shown with the pituitary gland and the hypothalamus highlighted.