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The
Periodic Cycle of a Woman
What is the female
periodic cycle
The normal reproductive years of
the female are characterized by monthly rhythmic changes in the rates of
secretion of the female hormones and corresponding changes in the ovaries
and sexual organs as well. This rhythmic pattern is called the female sexual
cycle. The duration of the cycle averages 28 days.
Which hormones govern
the female cycle
The Female hormonal system consist
of five hormones –
-
Luteinizing hormone releasing hormone
(LHRH)
-
Follicle stimulating hormone (FSH):
FSH stimulates the ovaries and growing follicles.
-
Luteinizing hormone (LH): LH stimulates
ovulation
-
Estrogen: It is responsible for regulating
and sustaining female sexual development and reproductive function.
-
Progesterone: It prepares endometrium
for implantation.
How are ovulation
and menstrual cycle defined
Ovulation is the result of a complex
series of events leading to the production and release of an egg. If that
egg is fertilized and gets implanted in the lining of the uterus wall (endometrium)
a pregnancy has commenced. If it is not fertilized, then it is lost together
with the endometrium as the menstrual blood flow at the beginning of your
next period. These events are collectively known as the Menstrual Cycle
and are controlled by a pea-sized structure called the pituitary gland,
which is attached to the undersurface of the brain.
What happens during
the menstrual cycle?
-
At the beginning of a period, a hormone
called Follicle Stimulating Hormone (FSH) is released from the pituitary
gland. FSH stimulates a follicle, on the surface of the ovary, to grow.
Contained within the follicle is the developing egg.
-
During the next two weeks the egg grows
and matures, and as it does so, a female hormone called estrogen is produced
in increasing quantities by the ovary. The estrogen in turn enters the
bloodstream and feeds back to a part of the brain above the pituitary gland
where it is recognized by special receptors. If enough estrogen has been
produced, this feed back process decreases the production of FSH.
-
Rising estrogen levels also trigger
the output of another hormone from the pituitary gland called Luteinizing
Hormone (LH). This leads to the release of the mature egg from the follicle.
The escape of the egg from the ovary is known as ovulation.
-
After ovulation, the empty follicle
forms a structure called the corpus luteum, which produces the second female
hormone, called progesterone. The progesterone levels go up after ovulation,
and maintain the endometrium in a state of readiness to receive a fertilized
egg. If the fertilized egg does not implant itself in the endometrium,
the progesterone level falls and a period commences. The whole cycle now
begins once more.
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