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Monthly Cycle
Menopause Oasis
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Which glands / body parts and which hormones govern our monthly menstrual cycle?

Anatomy of a monthly menstrual cycle:

The glands involved and what they produce:

Hypothalamus. A gland in the brain that is responsible for regulating the body's thirst, hunger, sleep patterns, libido and endocrine functions. This gland produces Gonadotropin Releasing Hormone (GnRH) at the end of your monthly cycle as your estrogen levels decrease. This in turn stimulates the production of Follicle Stimulating Hormone Releasing Factor (FSH-RF) to tell the pituitary, another gland in the brain, to do its job. Thus the cycle begins again.

Pituitary. This gland secretes Follicle Stimulating Hormone (FSH) and a little Leutenizing Hormone (LH) into the bloodstream which cause follicles to begin to mature.

Ovaries.  These glands, located one on either side of the abdomen below the waist, produce the ova (eggs), and female hormones. 


The hormones that are produced by your body and how they effect your periods:

Estrogen is produced by maturing Ovarian follicles. As the follicles ripen over a period of about seven days, they secrete estrogen into the bloodstream. This causes the lining of the uterus to thicken. It causes the cervical mucous to change. When estrogen level reaches a certain point it causes the Hypothalmus to release LH-RF causing the pituitary to release a large amount of LH. This surge of LH triggers the one most mature follicle to burst open and release an egg. This is called ovulation.

Androgen is produced by the follicle cells in the ovary and is converted into additional estrogen. Androgen causes the disappearance of all of the follicles not destined to produce an egg during a given monthly cycle

Progesterone is produced by the corpus luteum (the follicle that has just ruptured to provide a viable egg). Progesterone causes the endometrium (the surface of the uterine lining) to become covered with mucous, secreted from glands within the lining itself. If fertilization and implantation do occur the corpus luteum continues to product progesterone for up to three months until the placenta can fend for itself. Otherwise the corpus luteum ceases production of progesterone and the spiral arteries of the uterine lining close off, stopping blood flow to the surface of the lining. The left over blood, along with the endometrial lining is then shed, forming the menstrual flow.


The Process itself:

The hypothalmus releases FSH-RF to tell the pituitary gland to secrete FS and a little LH into the bloodstream causing the follicles to begin to mature.

These maturing follicles then release estrogen in increasing amounts for about seven days. This causes the lining of the uterus to thicken and the cervical mucous to change. When the estrogen level reaches a certain point the hypothalmus releases more LH-RF causing the pituitary to release a large amount of LH. This surge of LH triggers the one most mature follicle to burst open and release an egg. This is called ovulation. [Many birth control pills work by blocking this LH surge, thus inhibiting the release of an egg.]

As ovulation approaches, the blood supply to the ovary increases and the ligaments contract, pulling the ovary closer to the Fallopian tube. This allows the egg, once released, to find its way into the tube. During this time a woman's cervix secretes an abundance of clear "fertile mucous" which is characteristically stretchy. Fertile mucous facilitates the sperm's movement toward the egg.

Once inside the Fallopian tube, the egg is carried along by tiny, hairlike "cilia" toward the uterus. Fertilization occurs if sperm are present as the live egg reaches the uterus.

The follicle from which the egg burst becomes the corpus luteum (yellow body). As it heals, it produces estrogen and, in larger amounts, progesterone which is necessary for the maintenance of a pregnancy. This abundance of progesterone causes the endometrium (the lining of the uterus), to become covered with mucous that is secreted from glands within the lining itself.

If conception occurs, Human Chorionic Gonadotropin (HCG) from the developing placenta takes over, continuing production of progesterone. High progesterone levels shut down production of GnRH, leaving HCG in control for the duration of the pregnancy.

If fertilization and implantation do not occur, the corpus luteum dies and turns white and is then known as the corpus albicans. This event causes an abrupt drop in the production of both estrogen and progesterone and the blood which has built up, along with the endometrial lining, are shed in the form the menstrual flow.

And the cycle begins anew.

Female Reproductive System

Falopian tubes:  Provide a pathway for the egg to travel to the uterus.
Ovaries:  Produce the ova (eggs), estrogen, progesterone and androgen/testosterone.
Uterus:  (Womb) Provides a home in which a fertilized egg develops into an infant.  The lining, if a woman does not become pregnant, sloughs off and is shed - the menstrual flow.
Cervix:  The lower third of the uterus and the opening of the uterus into the vaginal canal.
Vagina:  The muscular tube that connects the uterus to the outside of the body.  (The birth canal)

Abnormal or Unusual Bleeding
You will see us, many times, caution that "all abnormal or unusual bleeding should be checked by your doctor".
So, what is considered "abnormal"?  Here are a couple of Web sites that explain this quite completely.  The first, Healthy Women, explains it quite clearly - in terms easily understood.  The second, WebMD, delves into the medical terminology a bit more, but is very informative!