The menstrual cycle describes the monthly process a woman's body goes through to prepare for potential pregnancy. If pregnancy does not occur, the thickened uterine lining breaks down and is discharged as menstruation. The cycle is initiated by hormones that cause an egg to mature in one of the ovaries each month. If the egg is fertilized by a sperm, pregnancy will occur. Otherwise, without hormones to sustain it, the uterine lining breaks down and is shed, completing the cycle and preparing the body for the next potential pregnancy.

1. Menstrual Cycle
Objectives:
-Explain the process of menstrual
cycle.
-Describe the menstrual cycle.

2. 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

3. 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

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

5. 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

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

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

8. 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

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

10. 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

11. 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

12. 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

13. 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

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

16. References:
The world of Science 5
Into the Future; Science and Health 5
BEC Handbook in Science 5
Encarta 2009