# Ovarian Cycle --- The **ovarian cycle** is one part of the [[menstrual cycle]] that describes what is happening inside the ovaries. It is the [[oocyte]] maturation process that takes place in the [[ovaries]], where once every 28 days (or so) a single follicle is *ejected* from the ovary, and picked up and brought into the [[uterus|uterine tubes]]. The ovarian cycle is divided into three phases, the follicular phase, ovulation, and the luteal phase. The **follicular phase** takes place between days 1 and 13 of the ovarian cycle, and during this time a [[ovarian follicle|primordial follicle]] matures. The granulosa cells divide a lot, thickening the outside of the follicles, they release hormones, and a fluid-filled space called the antrium develops. The oocyte resumes meiosis, and completes meiosis I (one daughter cell is discarded and undergoes atresia, while the other oocyte continues to be nourished), and it is now considered a secondary oocyte. The mature follicle is so big by the end of day 13 that it forms a bulge on the outside of the ovary. Ovulation takes place on the 14th day of the ovarian cycle. This is where the outside wall of the follicle/ovary bursts open to eject the secondary oocyte out of the ovary. The fimbriae of the ovarian tubes collect it and bring it into the lumen of the tubes where it travels down toward the uterus. The luteal phase takes place during days 15-28, and is when the follicle that is left behind becomes a structure called a corpus luteum. The corpus luteum continues to secrete progesterone and estrogen (in order to build up the uterine lining in case the ovulated egg becomes fertilized and will need a good place to implant), and also inhibin (which prevents the hypothalamus/anterior pituitary gland from secreting any more gonadotropins). ![[ovarian cycle.png]] - **ovarian cycle**: three phases - **follicular phase**: days 1-11 - in the beginning, oocyte and follicule cells stimulate ~20 primordial follicles to become primary follicles by **FSH** and **LH** - as this keeps going, start to release hormone **inhibin** to inhibit FSH production - becomes **mature follicle** - **ovulation**: day 14 - induced by peak **LH** secretion - increased fluid production which eventually bursts out of the ovary wall - leaves behind a **corpus luteum** (yellow body) - eventually becomes scar tissue/**white body** - **luteal phase**: 15-28 - this is always 14 days long. does not matter how long the cycle is as a whole, the luteal phase lasts 14 days. - **corpus luteum** from ovulation becomes a temporary *endocrine gland* - secretes **progesterone** and **estrogen** to stabilize/build up uterine lining - secretes **inhibin** to inhibit hypothalamus and anterior pituitary from secreting reproductive hormones - if not pregnant, keeps going for about 14 days, then mensuration - if pregnant, keeps going for ~3 months - gets signals from trophoblast cells [[human chorionic gonadotropin|hCG]] hormone - this is what a pregnancy test looks for - then it stops when [[placenta]] takes over - **menstration**: as corpus luteum stops secreting hormones over the course of ~10-13 days if the egg is not fertalized, the unterine lining sheds. - **menses** shed lining - **menopause** - typically 45-55 - no more follicles, or they have stopped maturing ## Fertile Period •Ovum is viable 24 hours •Sperm is viable up 5 days •Ovulation occurs around day 14 in the 28 day cycle, or 14 days before the start of the next menstrual cycle •Signs of ovulation: LH surge, cervical mucus changes, basal body temperature changes [[fertilization]] ___