StepS (results): 1-Amniotic cavity expansion leads to primitive umbilical ring formation by ventral shifting of amnio-ectodermal junction towards endoderm. 9- Reversal of position; a) Heart & pericardium become cranial to septum transversum b)Connecting stalk & allantois become ventral & cranial to cloacal membrane.6- Formation of definitive yolk sac (yolk sac part remaining outside abdomen in umbilical cord) & midgut is connected to it by vitelline duct.5-Part of yolk sac is incorporated inside folded embryo leading to gut formation;

foregut in head fold, midgut in middle & hindgut in tail fold.4-Embryonic disc elongation leads to cephalo-caudal folding with head & tail folds.7- Peritoneal canals of intraembryonic coelom surround gut with mesenteries formation.Ring

contains connecting stalk, allantois & vitelline duct.2- Embryonic disc bulges in amniotic cavity to be completely surrounded by it.

3-Embryonic disc changes into cylindrical shape with body cavity.8- Formation of forebrain bulge in head fold which is separated from pericardial bulge b stomodeum.Buccopharyngeal membrane separates stomodeum from foregut.Chorion