Anovulatory cycle
While the normal menstrual cycle in the human typically lasts 4 weeks (28 days, range 24–35 days) and consists of a follicular phase, ovulation, and a luteal phase, followed by either menstruation or pregnancy, the anovulatory cycle has cycle
lengths of varying degrees. In many circumstances, menstrual intervals are prolonged exceeding 35 days leading to oligomenorrhea (cycle >35 – 180 days interval), or even longer, amenorrhea. In other cases, menstruation may be fairly regular (eumenorrhea), or more frequent (intervals < 21 days), or there may be a loss of menstrual pattern (menorrhagia, dysfunctional uterine bleeding).
Human sexuality
Ovulation is based on a monthly cycle; the 14th day is the most fertile. On days one to four, menstruation and production of estrogen and progesterone decreases, and the endometrium starts thinning. The endometrium is sloughed off for the next three to six days. Once menstruation ends, the cycle begins again with an FSH surge from the pituitary gland. Days five to thirteen are known as the pre-ovulatory stage. During this stage, the pituitary gland secretes follicle-stimulating hormone (FSH). A negative feedback loop is enacted when estrogen is secreted to inhibit the release of FSH. Estrogen thickens the endometrium of the uterus. A surge of Luteinizing Hormone (LH) triggers ovulation. On day 14, the LH surge causes a Graafian follicle to surface the ovary. The follicle ruptures and the ripe ovum is expelled into the abdominal cavity. The fallopian tubes pick up the ovum with the fimbria. The cervical mucus changes to aid the movement of sperm. On days 15 to 28—the post-ovulatory stage, the Graafian follicle—now called the corpus luteum—secretes estrogen. Production of progesterone increases, inhibiting LH release. The endometrium thickens to prepare for implantation, and the ovum travels down the Fallopian tubes to the uterus. If the ovum is not fertilized and does not implant, menstruation begins.