Menstrual Cycle

Objectives:

-Explain the process of menstrual cycle. -Describe the menstrual cycle.

Menstruation is a periodic vaginal discharge in humans and other mammals, consisting of blood and cells shed from the endometrial, or lining of the uterus.

Menstrual Cycle

Menstruation accompanies a woman's childbearing years, that begins between the ages of 10 and 16, at puberty, and most often ceasing between the ages of 45 and 50, at menopause.

Menstrual Cycle

Menstruation is part of the process that prepares a woman for pregnancy.

Menstrual Cycle

Each month the lining of the uterus thickens; if pregnancy does not occur, this lining breaks down and is discharged through the vagina.

Menstrual Cycle

In most women the menstrual cycle is about 28 days, but it can vary considerably even from one month to another.

Menstrual Cycle

The cycle is initiated by hormones in the blood that stimulate the ovaries (the two female organs that produce ova, or eggs).

Menstrual Cycle

The hormones cause an egg in one of the two ovaries to mature (to become capable of being fertilized and develop into a fetus).

Menstrual Cycle

The ovaries also produce hormones of their own, primarily estrogen, which cause the endometrium to thicken.

Menstrual Cycle

The egg passes through the fallopian tube to the uterus. If the egg unites with a sperm on its way to the uterus, fertilization occurs and pregnancy ensues.

Menstrual Cycle

If fertilization does not occur, the lining of the uterus does not receive the hormones it needs to continue the thickening process. Thus, the uterine lining breaks down and is discharged from the body during menstruation.

Menstrual Cycle

Many women experience premenstrual discomfort. Tenderness of the breasts and a tendency to retain fluid (bloat) are common one to seven days before each period.

Menstrual Cycle

Some women also experience a condition called premenstrual syndrome which is characterized by headaches, irritability, nervousness, fatigue, crying spells, and depression with no apparent cause.

Menstrual Cycle

A few women also experience menstrual cramps (dysmenorrhea) during the first day or two of the period.

Menstrual Cycle

References:

The world of Science 5

Into the Future; Science and Health 5

BEC Handbook in Science 5

Encarta 2009