The chorioallantoic membrane (CAM) is an essential structure in amniotic vertebrates that serves as a respiratory organ during embryonic development, formed from the fusion of the allantois and chorion.
Research on chicken embryos revealed that CAM fusion starts when the allantois reaches a diameter of about 2.5-3.0 mm, occurring in approximately 6 hours, and involves a transition from an epithelial mesothelial layer to a fused structure.
Similar fusion processes were observed in primates, indicating potential common mechanisms across amniotes, with a call for further investigation into the cellular dynamics of CAM formation.