Female Reproductive System (cont.)
Ovulatory Phase
The ovulatory phase, or ovulation, starts about 14 days after the follicular
phase started. The ovulatory phase is the midpoint of the menstrual cycle, with
the next menstrual period starting about 2 weeks later. During this phase, the
following events occur:
- The rise in estrogen from the dominant follicle triggers a surge in the amount of luteinizing
hormone that is produced by the brain.
- This causes the dominant follicle to release its egg from the ovary.
- As the egg is released (a process called ovulation) it is captured by
finger-like projections on the end of the fallopian tubes (fimbriae). The
fimbriae sweep the egg into the tube.
- Also during this phase, there is an increase in the amount and a change in
the consistency of mucus produced by the cervix (lower part of the uterus.) If a
woman were to have intercourse during this time, this receptive mucus captures
the man's sperm, nourishes it, and helps it to move towards the egg for
fertilization.
Luteal Phase
The luteal phase begins right after ovulation and involves the following processes:
- Once it releases its egg, the empty follicle develops into a new structure
called the corpus luteum.
- The corpus luteum secretes the hormone
progesterone. Progesterone prepares the uterus for a fertilized egg to implant.
-
If intercourse has taken place and a man's sperm has fertilized the egg (a
process called conception), the fertilized egg (embryo) will travel through the
fallopian tube to implant in the uterus. The woman is now considered pregnant.
-
If the egg is not fertilized, it passes through the uterus. Not needed to
support a pregnancy, the lining of the uterus breaks down and sheds, and the
next menstrual period begins.
How Many Eggs Does a Woman Have?
During fetal life, there are about 6 million to 7 million eggs. From this time, no new eggs are produced.
The vast majority of the eggs within the ovaries steadily die, until they are depleted at menopause.
At birth, there are approximately 1 million eggs; and by the time of puberty,
only about 300,000 remain. Of these, 300 to 400 will be ovulated during a
woman's reproductive lifetime. The eggs continue to degenerate during pregnancy,
with the use of birth control pills, and in the presence or absence of regular
menstrual cycles.
Reviewed by the doctors at The Cleveland Clinic Department of Obstetrics and Gynecology.
Edited by Cynthia Haines, MD,
January 2006.
Portions of this page copyright © The Cleveland Clinic 2000-2004
Last Editorial Review: 1/31/2005 8:18:18 AM
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