The caudal end of the embryo is at first connected to the chorion by a band of mesoderm called the body-stalk, but with the formation of the caudal fold the body-stalk assumes a ventral position; a diverticulum of the yolk-sac extends into the tail fold and is termed the hind-gut.
The function of the body-stalk is later replaced by the umbilical cord.
Additional images
Human embryo—length, 2 mm. Dorsal view, with the amnion laid open. X 30.
Human embryo of 2.6 mm.
Diagram showing later stage of allantoic development with commencing constriction of the yolk-sac.
Model of human embryo 1.3 mm. long.
Section through ovum imbedded in the uterine decidua.
Embryo between eighteen and twenty-one days.
Human embryo about fifteen days old. Brain and heart represented from right side. Digestive tube and yolk sac in median section.
