Ovulation is the release of eggs in the middle of each menstrual cycle. It involves the release of a mature egg from the ovary and pushing it down through the Fallopian tubes in order to make the egg available for fertilization. In humans, a single ovary matures an egg per one time.
The development of an egg inside the ovary is stimulated by FSH follicle-stimulating hormone , a type of gonadotrophin produced by the anterior pituitary. FSH also stimulates the production of estrogen by the ovary.
Estrogen is responsible for preparing the uterus for the fertilization event. The levels of estrogen are low at the beginning of the menstrual cycle, but they gradually rise with the development of the follicle. High levels of estrogen stimulate the production of fertile cervical mucus. The rapid elevation of the levels of LH luteinizing hormone stimulates the rupture of the developed follicle, releasing the egg.
The released egg from the ovary can survive only for 24 hours inside the female reproductive system. Thereby, the day of ovulation is the most fertile day in the menstrual cycle. However, since sperms can survive days inside the female reproductive system, the fertile period of the menstrual cycle is known as the fertile window.
In addition, the ruptured follicle in the ovary starts to produce progesterone, which builds up the uterus wall. During the period, the pituitary gland a small area at the base of the brain that makes hormones produces a hormone called follicle stimulating hormone FSH.
FSH tells the ovaries to prepare an egg for ovulation release of an egg from the ovary. Throughout the menstrual cycle, there are multiple follicles fluid filled sacs containing eggs in each ovary at different stages of development 5,6.
About halfway through the follicular phase just as the period is ending one follicle in one of the ovaries is the largest of all the follicles at about 1 cm 0. This follicle becomes the dominant follicle and is the one prepared to be released at ovulation. The dominant follicle produces estrogen as it grows 8 , which peaks just before ovulation happens 7.
For most people, the follicular phase lasts days, but this can vary from cycle-to-cycle 4. When: From the end of the period until ovulation. What: The uterus builds up a thick inner lining. While the ovaries are working on developing the egg-containing follicles, the uterus is responding to the estrogen produced by the follicles, rebuilding the lining that was just shed during the last period.
This is called the proliferative phase because the endometrium the lining of the uterus becomes thicker. The endometrium is thinnest during the period, and thickens throughout this phase until ovulation occurs 9. The uterus does this to create a place where a potential fertilized egg can implant and grow When: About midway through the cycle, but this can change cycle-to-cycle. Ovulation divides the two phases of the ovarian cycle the follicular phase and the luteal phase.
What: An egg is released from the ovary into the fallopian tube. The dominant follicle in the ovary produces more and more estrogen as it grows larger. The dominant follicle reaches about 2 cm 0.
When estrogen levels are high enough, they signal to the brain causing a dramatic increase in luteinizing hormone LH This spike is what causes ovulation release of the egg from the ovary to occur. Ovulation usually happens about days before the start of the next period When: From ovulation until the start of the next period. What: The sac that contained the egg produces estrogen and progesterone. Once ovulation occurs, the follicle that contained the egg transforms into something called a corpus luteum and begins to produce progesterone as well as estrogen 10, Progesterone levels peak about halfway through this phase The hormonal changes of the luteal phase are associated with common premenstrual symptoms that many people experience, such as mood changes, headaches, acne, bloating, and breast tenderness.
If an egg is fertilized, progesterone from the corpus luteum supports the early pregnancy If no fertilization occurs, the corpus luteum will start to break down between 9 and 11 days after ovulation This results in a drop in estrogen and progesterone levels, which causes menstruation.
The ovulation phase is the only time during your menstrual cycle when you can get pregnant. Ovulation happens at around day 14 if you have a day cycle — right in the middle of your menstrual cycle. It lasts about 24 hours. Because sperm can live up to five days, pregnancy can occur if a woman has sex as much as five days prior to ovulation.
After the follicle releases its egg, it changes into the corpus luteum. This structure releases hormones, mainly progesterone and some estrogen. The rise in hormones keeps your uterine lining thick and ready for a fertilized egg to implant.
If you do get pregnant, your body will produce human chorionic gonadotropin hCG. This is the hormone pregnancy tests detect. It helps maintain the corpus luteum and keeps the uterine lining thick.
This leads to decreased levels of estrogen and progesterone, which causes the onset of your period. The uterine lining will shed during your period. These include:. The luteal phase lasts for 11 to 17 days. The average length is 14 days. Some women get their period at the same time each month. Others are more irregular. Some women bleed more heavily or for a longer number of days than others.
Your menstrual cycle can also change during certain times of your life. For example, it can get more irregular as you get close to menopause. Write down when they start and end. Also record any changes to the amount or number of days you bleed, and whether you have spotting between periods. If you have these or other problems with your menstrual cycle or periods, talk to your healthcare provider. Be alert for any changes, and report them to your healthcare provider.
Worried about a late period, but know you aren't pregnant?
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