How does a woman ovulate?
Ovulation is the most fertile period of a woman's cycle, her prime time to try when attempting conception. Understanding how a woman ovulates can give you a deeper grasp of your body functions and help in getting pregnant. Using our ovulation calendar can help you pin point when you are ovulating to help you get pregnant.
Physiological changes when a woman ovulates.
On or about the fifteenth day of an ideal 28 day cycle, the preovulatory follicle releases a mature ovum into the oviduct to be fertilized. This is known as Ovulation. Ovulation requires the collective actions of the preovulatory surges of LH and FSH. When a woman ovulates, the maturation of the ovum also requires the LH surge.
After a resting state, the oocyte in the preovulatory follicle resumes meiosis during the ovulation sequence. The oocyte nucleus or germinal vesicle undergoes a series of changes that involve germinal vesicle breakdown (GVBD), and the progression of meiosis to the second meiotic metaphase or first polar body stage. Meiosis is arrested here and will proceed no further unless the ovulated egg is fertilized. Meiotic maturation is a vital event in ovulation because it is obligatory for normal fertilization. The LH/FSH surge in some way causes meiotic maturation by desensitization and down regulation of the LH and FSH receptors.
Perhaps the most dramatic change during ovulation concerns the formation of a hole in the ovary surface, the stigma. This is the spot where the fertilized ovum is implanted. During this process, the follicle produces proteases that degrade the ovarian tissues. LH has been shown to be directly involved in stigma formation. In response to the LH surge, the preovulatory follicle produces progesterone and prostaglandin, both of which are obligatory for the stigma to develop. And so anovulation in women is a failure of dominant follicles to ovulate because stigma formation is compromised. How LH-induced progesterone and prostaglandin production come together to form the stigma remains unknown.
The Hormones in action when a woman ovulates.
When a woman ovulates, various hormones in her body are synchronized to prepare her for ovulation, fertilization and implantation. Ovulation occurs approximately 10-12 hours after the LH peak.
Here are the primary hormones involved in ovulation in women:
- Progesterone - The ovaries produce significant amounts of progesterone during the 2 weeks or so that follow ovulation. Progesterone thickens the nutrient-rich endometrium in preparation to receive a fertilized egg. It also acts on the breasts to prepare them for milk production (lactation).
- Estrogen – Estrogen is produced in increasing quantities prior to ovulation, helps the uterus rebuild its lining (or endometrium) after menstruation. In addition, estrogen and progesterone also act as feedback controls on the brain hormones LH and FSH. In other words, these sex hormones travel to the brain to increase or decrease LH and FSH production. This feedback mechanism helps to regulate the timing and the events of the menstrual cycle.
- Estrogen and progesterone are both made primarily in the ovaries from cholesterol. Initially, the ovaries use cholesterol to derive progesterone and the male sex hormone testosterone. Then the ovaries convert a good portion of the progesterone and almost all of the testosterone into estrogen. After ovulation occurs, more progesterone is made than can be converted; consequently, significant amounts of progesterone are secreted only during the latter half of the cycle.
- LH- The LH surge is initiated by a dramatic rise of estradiol produced by the preovulatory follicle. The LH surge occurs 34 to 36 hours prior to ovulation and is a relatively precise predictor for timing ovulation. The LH surge stimulates luteinization and stimulates the synthesis of progesterone responsible for the mid cycle FSH surge. Also, the LH surge stimulates resumption of meiosis and release of ovum.
- FSH- Estradiol levels fall dramatically immediately prior to the LH peak. Elevated FSH levels at this time are thought to free the ovum from the follicular attachments. Progesterone is responsible for stimulating the mid cycle rise in FSH. The mechanism causing the postovulatory fall in LH is unknown. The decline in LH may be due to the loss of the positive feedback effect of estrogen, due to the increasing inhibitory feedback effect of progesterone, or due to a depletion of LH content of the pituitary from downregulation of GnRH receptors.
Find out what is ovulation and what are the physical signs of ovulation.
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