 | ||
|
| |    Menstrual Cycle Basics by Marjorie Greenfield, M.D. reviewed by Marjorie Greenfield, M.D. Whether viewed as a benchmark of womanhood, a necessary annoyance, or a mortifying embarrassment, the menstrual period has emotional and practical meaning for most women. In the United States, the average age for the first period or menarche (pronounced men-ark-ee) is 12 years. Once cycles are established, most periods last 3 to 7 days. The average cycle (counting from the first day of one period to the first day of the next) is 28 days, although anything between 24 and 35 days is normal. The average age for the final menstrual period (commonly known as the menopause) is 51. At menarche, we learn how to deal with our period discreetly. Over the years, we often welcome it as a sign that all systems are working properly, and we may mourn or celebrate (or both) when it finally is gone for good. Overview of the menstrual cycle During the course of a month, a woman's uterine lining (endometrium) will go through predictable changes as it creates an environment that can support an early embryo. When the embryo doesn't implant, the lining sheds in its hopeful quest to ready itself for the next ovulation. The first half of the month In the first part of the menstrual cycle, right after the period, the predominant circulating female hormone is estrogen, made by the ovary as the eggs start to mature. Estrogen stimulates the uterine lining to heal over (from the last period), and thicken. When under the effects of estrogen, the lining of the uterus is said to be in the "proliferative phase." The second half of the month After ovulation, the predominant ovarian hormone is progesterone (pro-=for, -gesterone=gestation or pregnancy.) Progesterone causes the lining of the uterus to get ready for the implantation of a fertilized egg. During its two weeks of progesterone exposure, the lining of the uterus is said to be in "secretory phase." What starts menstruation? The ovary stops making progesterone about 14 days after ovulation, if conception has not occurred (meaning that there is no early embryo making the pregnancy hormone hCG.) The drop in progesterone level allows the uterine lining to begin to shed, which exposes small blood vessels and starts the period. The menstrual flow includes the surface layers of the uterine lining, blood cells, and sometimes, small blood clots. What stops menstruation? Bleeding continues until the blood's clotting mechanisms plug up the tiny blood vessels, and, from the rise in estrogen levels at the start of the next ovulation cycle, the endometrial surface heals over. Then the whole cycle starts again.
| |  | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| About Us |
Contact Us |
Our Partners Privacy Policy | Ethics | Advertising Policy | Terms of Service © Copyright 2004 The Dr. Spock Company. All Rights Reserved. THIS SITE DOES NOT PROVIDE MEDICAL ADVICE. The information drSpock.com
provides is for educational purposes only and is not a substitute for
professional medical advice. Always seek the advice of your health care
professional if you have a specific health concern. Mention or advertisement
of any product, service, or brand does not constitute endorsement, guarantee,
or recommendation by The Dr. Spock Company. Please read our full
Terms of Service. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
