Instead of preparing to form fingers and toes and a brain like the rest of the embryo's cells, these ones are destined to form a disc - shaped organ that's chock - full of blood vessels and will take over for the corpus luteum in the second trimester: the placenta. (whattoexpect.com)
Progesterone is a hormone released by the corpus luteum in the ovary. (holtorfmed.com)
The empty follicle becomes the corpus luteum which is responsible for producing progesterone. (longibbons.com)