Overview
The process of ovulation is controlled by the hypothalamus of the brain and through the release of hormones secreted in the anterior lobe of the pituitary gland, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). In the pre-ovulatory phase of the menstrual cycle, the ovarian follicle will undergo a series of transformations called cumulus expansion, which is stimulated by FSH. After this is done, a hole called the stigma will form in the follicle, and the ovum will leave the follicle through this hole. Ovulation is triggered by a spike in the amount of FSH and LH released from the pituitary gland. During the luteal (post-ovulatory) phase, the ovum will travel through the fallopian tubes toward the uterus. If fertilized by a sperm, it may perform implantation there 6–12 days later.
Ovulation occurs when a mature egg is released from the ovary into the oviduct. Afterwards, it will eventually become available to be fertilized. Concomitantly, the lining of the uterus is thickened to be able to receive a fertilized egg. If no conception occurs, the uterine lining as well as blood will be shed in menstruation.
In humans, the few days near ovulation constitute the fertile phase. The time from the beginning of the last menstrual period (LMP) until ovulation is, on average, 14.6 days, but with substantial variation both between women and between cycles in any single woman, with an overall 95% prediction interval of 8.2 to 20.5 days.
Cycle length alone is not a reliable indicator of the day of ovulation. While in general an earlier ovulation will result in a shorter menstrual cycle, and vice versa, the luteal (post-ovulatory) phase of the menstrual cycle may vary by up to a week between women.
Read more about this topic: Ovulation