Extraembryonic membrane development
Embryo is surround by amnion
Sac fill with amniotic fluid
Chorion form outside amnion
Chorionic villi and uterine lining to form placenta
Nutrient and oxygen from mother diffuse across thin membrane from mother blood to embryo blood.
Fetus
eight weeks of development
Most organ and tissue of fetus is fully form
Fetus may begin to move
Weight ~28 grams and only ~ 8 cm. long