The corpus luteum is a temporary endocrine structure that forms in the ovary after ovulation. It is a yellowish, mass of cells that develops from the ruptured follicle that released the egg during ovulation. The corpus luteum secretes hormones such as progesterone, which helps prepare the uterus for possible implantation of a fertilized egg. If fertilization does not occur, the corpus luteum degenerates and turns into scar tissue known as the corpus albicans. If fertilization does occur, the corpus luteum continues to produce hormones to support the early stages of pregnancy until the placenta takes over hormone production.
