Answer:
To provide nourishment to the developing embryo.
Step-by-step explanation:
The heart starts functioning in the third week of embryo development. The heart is a circulatory organ. It supplies nutrients, oxygen to different cells and carries carbon dioxide, other waste materials from the embryo. The heart is the first organ to start functioning because it has to circulate blood which brings nourishment from the endothelial cells to other parts of the embryo. Otherwise, the embryo will die by depriving of oxygen. That's the very reason heart starts pumping first.