Embryology a science which study the processes and regulations of development of human fetus. ( from 1 ce( (zygote合子)to(57)×10cel) total 40/38 weeks: 280 /266 days 未次月经 的第一天受精 受精龄,266天 分 月经龄,280天▪ a science which study the processes and regulations of development of human fetus.(from 1 cell (zygote合子) to (5-7) x1012 cells) ▪ total 40/38 weeks: 280 /266 days 受精 分 娩 末次月经 的第一天 受精龄， 266天 月经龄， 280天 Embryology