Get answers to your menopause and sexual dysfunction questions.
The primary structures in the reproductive system are:
Typical Menstrual Cycle
Typical No. of Days
Follicular (Proliferative) Phase
Cycle Days 1 through 6: Beginning of menstruation to end of blood flow.
Estrogen and progesterone start out at their lowest levels.
FSH levels rise to stimulate maturity of follicles. Ovaries start producing estrogen and levels rise, while progesterone remains low.
Cycle Days 7 - 13: The endometrium (the inner lining of the uterus) thickens to prepare for the egg implantation.
Cycle Day 14:
Surge in LH. Largest follicle bursts and releases egg into fallopian tube.
Luteal (Secretory) Phase, also known as the Premenstrual Phase
Cycle Days 15 - 28:
Ruptured follicle develops into corpus luteum, which produces progesterone. Progesterone and estrogen stimulate blanket of blood vessels to prepare for egg implantation.
If fertilization occurs:
Fertilized egg attaches to blanket of blood vessels that supplies nutrients for the developing placenta. Corpus luteum continues to produce estrogen and progesterone.
If fertilization does not occur:
Corpus luteum deteriorates. Estrogen and progesterone levels drop. The blood vessel lining sloughs off and menstruation begins.
Onset of Menstruation (Menarche). The onset of menstruation, called the menarche, typically begins between the ages of 12 - 13 years. Menarche generally occurs 2 - 3 years after initial breast development (breast budding). African-American and Hispanic girls tend to mature slightly earlier than Caucasian girls. A higher body mass index (BMI) during childhood is associated with an earlier onset of puberty. Environmental factors and nutrition may also affect menarche timing.
Length of Monthly Cycle. The menstrual cycle can be very irregular during the first 1 - 2 years, ranging from 21 - 45 days. The length then generally stabilizes to an average of 28 days, although the cycle length may range from 21 - 34 days and still be considered normal. A variation of 10 days or more -- either more or fewer days -- may have an impact on fertility, however. When a woman reaches her 40s the cycle lengthens, reaching an average of 31 days by age 49. A number of factors can affect cycle length at any age.
Risk Factors for Shorter and Longer Cycles
Regular alcohol use
Being under 21 and over 44
Being very thin (also at risk for short bleeding periods)
Competitive athletics (also at risk for short bleeding periods)
Length of Periods. Periods average 6.6 days in adolescent girls. By the age of 21, menstrual bleeding averages 6 days until women approach menopause. However, about 5% of healthy women menstruate fewer than 4 days, and 5% menstruate more than 8 days.
Normal Absence of Menstruation. Normal absence of periods can occur in any woman under the following circumstances:
Perimenopause starts when the intervals between periods begin to lengthen, and it ends with menopause itself (the complete cessation of menstruation). Menopause usually occurs at about age 51, although smokers often go through menopause earlier.
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