a: Lateral view of a 4-week embryo showing the relationship of primordial gut to yolk sac. b: Drawing of median section of the embryo showing the early digestive system and its blood supply.

The yolk sac functions as nourishment for the developing embryo and can usually be seen by five-and-a-half to six weeks gestational age on a transvaginal ultrasound. Having a gestational sac doesn ...

Created from stem cells, without eggs, sperm, or a womb, the embryo model had a yolk sac and a proto-placenta, resembling a ...

respiratory and excretory exchange of material by diffusion between embryonic and maternal circulatory systems. The marsupials have a yolk sac placenta (the initial stage in the development of the ...

Scientists in Israel have grown synthetic embryo models of mice outside the ... master regulators of either the placenta or the yolk sac. Soon after being mixed together inside the device, the ...