Now, when we go from diagram two to diagram three, what happens is the upper portion of the hypoblast and the upper portion of the epiplast eventually migrates upward towards this pole, and we basically form the following diagram. So notice this entire green portion eventually develops into the umbilical vessel. Now, in nonhumans, it's called the yolksac. And the umbilical vesicle eventually becomes part of the umbilical cord system. And we also form this cavity that is created by the epiblast cells. And this is known as the amniotic cavity.