Ovarian Cycle
Cycle events that occur in the lining of the uterus make up the menstrual cycle. Cycle events that occur in the ovaries make up the ovarian cycle. The events of the ovarian cycle occur simultaneously with the menstrual cycle. Both cycles occur as a result of the interaction of the hormones FSH (follicle stimulating hormone), LH (lueteinizing hormone), estrogen, and progesterone.
The pituitary and hypothalamus glands regulate the reproductive system. The hypothalamus stimulates the pituitary to produce FSH and LH. FSH stimulates the development of the ovum. LH stimulates the release of the ovum from the ovary. The ovaries produce estrogen and progesterone in response to stimulation from FSH and LH.
There are several hundred thousand ova present in the female fetus after 12 weeks gestation. These are inactive until puberty. They are active from first menstruation until menopause.
Early in the ovarian cycle several ova (primary oocytes) are stimulated by FSH to mature. A follicle develops around the maturing ova. After a time one – and on occasion two – oocytes reach full maturity. Once the ovum is mature LH causes the follicle to rupture and the ovum is released from the ovary. This is called ovulation. The follicle remains behind in the ovary where it becomes a temporary gland. It lives as a temporary gland for approximately 14 days.
As the follicle develops it produces a hormone called estrogen. The more developed the follicle is the more estrogen it produces. The highest level (PEAK) of estrogen production is closely related to ovulation. Estrogen is responsible for mucus production and ovulation.
After ovulation the remaining follicle is called the corpus luteum and it produces a hormone called progesterone. Progesterone is the dominant hormone in the postovulatory
