Problem 7: Female Reproductive Cycle

Tutorial to help answer this question

In a "typical" 28 day female reproductive cycle, on which day following the beginning of the menstrual period is a women most likely to ovulate?
A. 7
B. 14
C. 21

Reproductive cycle

The first 12 days
For the first 12 days of the menstrual cycle, estrogen has a negative effect on the production of gonadotropins.

Following these 12 days the negative effect changes to a positive effect on the production of gonadotropic hormones.

This results in a small increase of follicle stimulating hormone (FSH), but a large increase of luteinizing hormone (LH).

This sudden increase of LH causes the mature follicle to release the egg. Following release of the ovum, the ruptured ovarian follicle develops into the corpus luteum.

End of the cycle
The corpus luteum, in turn, secretes estrogen and progesterone. These ovarian hormones are important for the maintenance of the endometrial lining of the uterus where the blastocyst implants itself.

Continued high levels of estrogen and progesterone produce a negative feedback on the secretion of gonadotropins by the anterior pituitary gland.

Natural family planning
This method can be effective at helping achieve a pregnancy as well as at avoiding one. It requires accurate and consistent charting of the menstrual cycle. Some of the factors that indicate fertility include basal body temperature, the position of the cervix, and observation of the cervical mucus. Indicators can be affected by illness, level of activity, stress, food, drugs, alcohol, and hormones.

To prevent pregnancy, abstinence is required during the fertile period. This method is not recommended for women with irregular menstrual cycles.

Failure rate
The failure rate for this method of birth control is 5% to 30% or effective rate of 70% to 95%.

The Biology Project
University of Arizona
Tuesday, February 10, 1998
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