The Stages of Human Embryonic Development

Stage 21 scaled logo  

Stage 21 embryos have a greatest length of 20 to 26.4 mm and an estimated post-fertilization age of approximately 49 to 52 days. At this stage the fingers become more elongated and the hands and feet approach each other. For the first time the cortical plate is present in the wall of the cerebral vesicle (hemisphere).

Stage 21 - lateral view of Carnegie specimen #7392