A stem-cell derived human embryo model showing blue cells (embryo), yellow cells (yolk sac) and pink cells (placenta). Scientists have grown an entity that closely resembles an early human embryo ...

Watch an ink injection into the yolk sac artery of a 72 hour-old chick embryo to reveal its beating heart vasculature. This was shot by Anna Franz using a reflected light microscopy technique in ...

This tissue forms sex cords which will develop into testes if the bird becomes a male or into the ovary if the bird becomes a female. Several thousand cells near the base of the yolk sac become very ...

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.

In a message shared with the Broncos' official website, Grossi said he had been diagnosed with a yolk sac tumor after ...