7th weeks
- The embryo measures 9 mm (1/4 inch) in length.
- Lens pits and optic cups form the start of the developing eye.
- Nasal pits form.
- The brain divides into 5 vesicles, including the early telencephalon.
- Leg buds form and hands form as flat paddles on the arms.
- Rudimentary blood moves through primitive vessels connecting to the yolk sac and chorionic membranes.
- The metanephros, precursor of the definitive kidney, starts to develop.
- The initial stomach differentiation begins