... The Human Embryo, Edited by Shigehito Yamada and Tetsuya Takakuwa p. cm. ISBN 978-953-51-0124-6 The Human Embryo 18Carnegie stage 23 Upper and lower limbs are well formed. They ... and Müller, 1987), while CS13 to CS23 were based on Kyoto Collection samples (Nishimura et al., 1968, Nishimura et al., 1974). THE HUMAN EMBRYO Edited by Shigehito Yamada and Tetsuya Takakuwa ... diameter and is surrounded by the zona pellucida. The second maturation division of the oocyte completes as the sperm penetrates the egg (fertilization). The sperm head and the nucleus of the oocyte...