Ovulation in Humans: When Does it Occur? What Triggers it?

Ovulation is defined as the release of an ovum or ova from the ovary. The ovulation period lasts for one day only.

Knowing what is the meaning of ovulation and what triggers it simply tells you how a new life can begin to evolve in a woman. The phenomenon is simply incredible.  In humans, a woman is born with about one million eggs in both her ovaries.

In humans, a woman is born with about one million eggs in both her ovaries. At puberty, about 400,000 eggs remain in both her ovaries. She begins to ovulate when she starts to menstruate at puberty. In her reproductive lifetime, a woman ovulates only about 300 to 400 eggs.

It is the day of ovulation and not the first day of your period that determines the length of the menstrual cycle.

Ovulation in humans

Ovulation is a process in which a single mature egg (ovum) is released from the ovarian follicle of one of the ovaries during each menstrual period.

An ovarian follicle is a cellular structure in the ovary in which an immature egg develops. There are many such ovarian follicles in the ovary. However, occasionally more than one egg may be released during ovulation.

Ovulation time is the most fertile period of the woman. This is the time during which she can become pregnant if she has had unprotected sex a little before or during the ovulation day and the sperm fertilizes the ovum or the egg.

The life of the ovum lasts only for 12 to 24 hours. Therefore, if the live sperm is present inside the reproductive organs of the woman during the ovulation day, conception can occur.

The fertile window period is, therefore, very small. If there is no active sperm to fertilize the egg, in those 12 to 24 hours, no conception will take place.

Conception usually occurs in the fallopian tube after which the fertilized egg travels down to the uterus to get implanted after 6 to 12 days.

There are about 15 to 20 such eggs, which develop in both the ovaries every month. The most mature egg among them is released from an ovary at the time of ovulation. The other eggs then recede and wither away.

There is no fixed pattern as to which ovary releases the egg and this is a fairly random process. It is not necessary that the ovaries do this in an alternate fashion.

Time of ovulation

The days surrounding the ovulation day are the most fertile days of the menstrual cycle. Those days fall from the 10th to the 18th day of the cycle and are taken considering the slight variation of ovulation day.

If you are not planning to get pregnant, you must avoid unprotected sex on these days of the menstrual month.

In humans, ovulation occurs about midway during the monthly menstrual cycle. In the usual 28 day cycle, it occurs on the 14th day. The first day of the ovulation cycle is the first day of your menstruation or the start of your period (bleeding).

But, variations occur from woman to woman and in the same woman month to month.

According to The American Pregnancy Association, ovulation can occur anytime between 11-21 days after the first day of your last menstrual period (LMP), or 12-16 days before you are expecting the next menstrual period to start.

What triggers ovulation?

Ovulation is induced or triggered by certain hormonal changes in the woman’s body. During menstruation, the levels of the sex hormones estrogen and progesterone are lowest.

The hypothalamus then messages the pituitary gland to secrete the follicular stimulating hormone (FSH), which triggers a few follicles in the ovaries to develop and form mature eggs.

The growing follicle secretes estrogen the level of which is at its peak when the ovum or egg is fully mature.

This peak secretion of estrogen brings about a surge of the luteinizing hormone (LH) from the pituitary gland of the brain.

This surge of LH triggers the release of the mature egg from the ovary. This release of the mature egg is called ovulation.

The uterine lining called the endometrium also thickens to receive the fertilized egg. If no conception occurs, the ovum dissolves, the hormonal levels decrease, and the endometrium and blood are shed during menstruation about 12 to 14 days after ovulation. The next cycle then restarts and this goes on every month.

 

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