EXTRA-EMBRYONIC-MEMBRANE.pdf

FORMATION OF THE EXTRA-EMBRYONIC MEMBRANE Peripheral portion of the germ layer give rise to the membrane which served as means of protection and a means of securing food from the blood of the mother. Because they are not incorporated in the body of the embryo and dis...

FORMATION OF THE EXTRA-EMBRYONIC MEMBRANE Peripheral portion of the germ layer give rise to the membrane which served as means of protection and a means of securing food from the blood of the mother. Because they are not incorporated in the body of the embryo and discarded at the time of birth, they’re called extra-embryonic membrane.  Extra-embryonic Membranes classified into: 1. Yolk sac - derived from splanchnopleure 2. Amnion derived from somatopleure 3. Chorion 4. Allantois - derived from splanchnopleure Yolk sac - part of the primitive gut which is not included within the body of the embryo. Absorbs from the uterus from its external surface - it directly covers the yolk Serves an organ purveying nutritive materials of the embryo. Amnion is attached to the body of the embryo where the body wall opens ventrally to the yolk stalk—fourth development, the opening become smaller to become the umbilical ring. Serves as protection against mechanical injury through the amniotic sac that enfolds the embryo.  Chorion – the outer layer of somatopleure. It expands quickly and by 7-8 days of incubation in the chick it becomes closely apposed to the inner shell membrane. Together with the allantois it mediates gas and water exchange Allantois—a diverticulum arises as soon as the hindgut of the embryo is established. Further developments take over the yolk sac to function for metabolic interchange between fetus and mother. As development proceeds, the yolk sac becomes smaller and the allantois gets bigger. Thank you for listening!