Learn about From Embryo to Fetus-Part One in this educational video from dizzo95.
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Male Speaker: Twenty days after fertilization, the embryo is a three layer disc of ectoderm, mesoderm, and endoderm cells. Eight days later the yoke sac is shrink the amnion has enlarged and the embryo has recognized above features. The embryo at three weeks has a primitive hard and rudimentary brain tissue, one week later the hardest pumping blood around the body and in to the placenta the embryo at five weeks has 28 pairs of tissue blocks, which later form bones and muscles, lymph buds and rudimentary eyes are visible and the tail is residing, one week later the hands and rudimentary fingers the eyes have lenses and the liver and heart are visible. At 7 weeks the head grows rapidly external ears are visible the eyes are opened and the tail has disappeared. At 8 weeks the embryo is now called the fetus; it has most of its tissues and organs and well developed hands and feet.