1. An amnion, chorion, and allantois are present during embryonic life. 2. In other words, the allantois takes no share in its formation. 3. Germ cells migrate from near the allantois and colonize the primordial gonads. 4. A very small allantois is found in modern amphibians. 5. Also, it is a common misconception that the allantois gives rise to the umbilical cord. 6. Tbx4 has been shown to be expressed in the allantois , hindlimb, lung and proctodeum. 7. Haeckel speculates that the allantois is formed in a similar way in both humans and other mammals. 8. The allantois ( 8 ) is a sac that collects the metabolic waste produced by the embryo. 9. The allantois regresses into the embryo to give rise to the urinary bladder and median umbilical ligament. 10. The first of these is the cranial portion which is continuous with the allantois and forms the bladder proper.
