Now there are two important functions of progesterone. First it is basically used to actually maintain that endometrium layer inside the uterus. And the second role is to basically inhibit the contraction of our smooth muscle in the uterus to basically prevent premature labor. Now let's move on to estrogen. So estrogen is initially released by the ovarian follicle, but when ovulation takes place, it's the corpus luteum that begins to release our estrogen. And finally, as the corpus luteum begins to break down, it's the placenta once again that takes over the role of releasing our estrogen.