An early tubular structure that pushes into and lies within the body stalk. Important allantoic (umbilical) blood vessels accompany the and extend to the chorion which becomes vascularized through their branches. The itself disappears by the fourth fetal month.
One of the membranes in the embryo, shaped like a sac, which grows out of the embryonic hindgut.
One of the extraembryonic membranes surrounding the developing fetus. Lying between the inner amnion and outer chorion, it carries blood from the fetus to the placenta and forms umbilical blood vessels.
The membranous sac that develops as an outgrowth of the embryonic hindgut. Its outer (mesodermal) layer carries blood vessels to the placenta and so forms part of the umbilical cord. Its cavity is small and becomes reduced further in size during fetal development.
A vascular structure which, very early in the life of an embryo, grows out from its hind-gut. The end becomes attached to the wall of the womb; it spreads out and becomes stalked, later developing into the placenta and umbilical cord, which forms the only connection between mother and embryo.
A transient embryonic structure that is the tubular outpouching from the bottom of the caudal end of the 3-week-old human embryo. Later, the allantois, its adjacent connecting stalk, and the yolk stalk merge to form the umbilical cord. The walls of the allantois give rise to the umbilical vein and arteries, and part of the cavity of the allantois remains as a tube, the urachus, that connects the developing bladder with the umbilical cord.
A membrane that extends from the yolk sac during the initial stages of embryo development, playing a role in the creation of the placenta and umbilical cord.