What happens to the Graafian follicle after ovulation?

After ovulation, the Graafian follicle turns into the corpus luteum, which secretes progesterone (and some estrogen); if pregnancy does not occur it regresses into the corpus albicans, but if pregnancy occurs it persists and supports early pregnancy.

In each menstrual (or estrous) cycle, a group of ovarian follicles begins to grow. One dominant follicle, called the Graafian follicle, matures and releases a secondary oocyte (the egg) during ovulation. This event is triggered by a surge of luteinizing hormone (LH). The story does not end when the egg leaves; the empty follicle now changes dramatically to become an endocrine gland.

Step-by-step changes after ovulation

1. Follicle rupture and oocyte release: The follicle wall thins and bursts; the oocyte surrounded by the corona radiata is released into the peritoneal cavity and is swept into the fallopian tube.
2. Luteinization of remaining follicle: The granulosa and theca cells of the ruptured follicle transform (under LH influence) into luteal cells. Blood and fibrin fill the collapsed cavity briefly, forming a small clot called the corpus hemorrhagicum.
3. Corpus luteum formation: Within a day or two, the temporary clot is organized and the structure becomes the corpus luteum (“yellow body”). It is highly vascular and rich in cholesterol for steroid synthesis.
4. Hormone secretion: The corpus luteum secretes progesterone and some estrogen. Progesterone prepares and maintains the uterine lining (endometrium) for possible implantation, decreases uterine contractions, and supports early embryo survival.

Two possible paths: with or without fertilization

Why progesterone from the corpus luteum is crucial

• Maintains endometrium: Keeps the uterine lining thick, secretory, and well-supplied with blood.
• Reduces uterine excitability: Lowers contractions that could dislodge an implanting embryo.
• Works with estrogen: Together they support glandular growth and nutrient-rich secretions.