Amniotic cavity 



Ainniotic cavity 



Adantois 



Amnion 

 Embryo 



^; Yolk sac 



^ — Extraembryonic 

 coelom 



Chorionic 

 villi 



15 DAYS 



Allantois 



-Yolk sac 

 — Embryo 



20 DAYS 



Yolk sac 



Amnion 



Amniotic cavity Extraembryonic 



coelom 

 30 DAYS 



I — Amnion 

 Extraembryonic Amniotic cavity 



coelom 



33 DAYS 



Figure 350. Diagrams of the early development of the human embryo surrounded by the 

 protective embryonic membranes. Note the rootlike villi which grow into the wall of the uterus. 



478 



