At 8.5 weeks, the embryo now resembles a human. Facial features continue to develop, the beginnings of external genitalia form, the anal passage opens although the rectal membrane is intact, circulation through the umbilical cord is well developed, and long bones begin to form.
Reviewed By: John D. Jacobson, MD, Department of Obstetrics and Gynecology, Loma Linda University School of Medicine, Loma Linda, CA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.