What happens when the ovary releases an egg in a normal adult female?

What Happens When the Ovary Releases an Egg in a Normal Adult Female

When the ovary releases an egg, a complex process called ovulation occurs, which involves hormonal triggers, follicular rupture, and release of the oocyte into the fallopian tube for potential fertilization. 1, 2

Hormonal Triggers and Follicular Development

• The ovulatory process begins with rising levels of follicle-stimulating hormone (FSH) from the anterior pituitary gland, which stimulates the development of ovarian follicles 2
• As follicles develop, one becomes dominant and continues to mature while producing increasing amounts of estrogen 1
• The rising estrogen levels eventually trigger a surge of luteinizing hormone (LH) from the pituitary gland, which initiates the final stages of ovulation 2, 3
• This LH surge triggers a cascade of molecular events within the ovary, including activation of epidermal growth factor (EGF)-like factors and steroid production 1

Cellular and Tissue Changes During Ovulation

• The LH surge induces the resumption of meiosis in the oocyte, which had been arrested since fetal development 2
• The follicle undergoes significant remodeling, with increased blood flow and production of prostaglandins 4
• The process resembles an inflammatory response, with the follicle becoming hyperemic (increased blood flow) 4
• Granulosa cells and cumulus cells surrounding the oocyte express immune-related proteins and cytokines such as interleukin-6 (IL-6) 4
• The cumulus cells surrounding the oocyte produce a hyaluronan-rich extracellular matrix, causing expansion of the cumulus-oocyte complex 4, 2

Follicular Rupture and Oocyte Release

• Proteolytic enzymes break down the follicular wall at the site of rupture 1, 3
• Contrary to previous beliefs, the oocyte remains relatively stationary during most of ovulation, only moving toward the rupture site minutes before its release 2
• The follicle ruptures, releasing the cumulus-oocyte complex into the peritoneal cavity where it is captured by the fimbriated end of the fallopian tube 1
• The entire process from LH surge to follicular rupture typically takes 24-36 hours 2

Post-Ovulatory Changes

• After ovulation, the remaining follicular cells transform into the corpus luteum, which produces progesterone to support potential pregnancy 3
• The luteal phase of the menstrual cycle begins, typically lasting about 11-14 days in women with normal cycles 5
• If fertilization does not occur, the corpus luteum degenerates, progesterone levels fall, and menstruation begins 3
• If fertilization occurs, the developing embryo produces human chorionic gonadotropin (hCG), which maintains the corpus luteum and its progesterone production 3

Cycle Characteristics and Fertility

• The fertile window spans approximately 6 days, ending on the day of ovulation 5
• Sexual activity during the cycle appears to influence cycle characteristics, with cycles involving intercourse showing longer luteal phases (11.4 days vs. 10.8 days), less premenstrual spotting, and more days of estrogen-stimulated cervical fluid 5
• These cycle characteristics associated with sexual activity suggest higher fecundability (probability of conception) 5

Clinical Implications

• Understanding the normal ovulatory process is essential for diagnosing and treating ovulatory disorders 1
• Defects in the ovulatory process are associated with various conditions of infertility or subfertility in women 1
• Knowledge of the ovulatory process informs fertility preservation techniques for women undergoing gonadotoxic treatments 6
• Timing of ovulation varies within and between women, influenced by factors such as age and parity 5