Now, let's move on to another extra embryonic membrane known as the umbilical vesicle. So in humans, the yolk sac is actually called umbilical vesicle because it doesn't actually contain any yolk. So what the umbilical vesicle of functions is, in early embryological development, it actually helps produce some of the red blood cells. So it produces some of the blood that the fetus actually contains. Now, the final extra embryonic membrane is the lantoise. So in non humans, this is a very important structure and it grows relatively large because what it does is it serves in waste disposal.