Ovulation, Menstruation and Fertilization: The Biology Basics

Ovulation is the process by which a mature egg is released from the ovary. Ovulation happens each month as a part of the menstrual cycle, and occurs approximately in the middle of the cycle days. The process of ovulation is triggered when the hormone FSH (Follicle Stimulating Hormone) is released by the pituitary gland.

Before actual ovulation occurs, hormones cause several follicles in the ovary to begin developing into mature eggs. As the follicles mature, usually one egg becomes dominant, and the others dissolve. The dominant egg is then released from the ovary, and travels down the fallopian tube. In the fallopian tube, the egg may be fertilized by sperm. If fertilization occurs, the egg becomes a zygote that can attach to uterine lining and develop into a fetus.

Ideally, a man’s sperm should have entered a woman’s body 24-36 hours before ovulation, so that the sperm has time to travel through the woman’s reproductive system to the newly-released egg. If the timing is right, the sperm will meet the egg as it journeys down the fallopian tubes, and fertilization occurs.

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After ovulation, a woman’s body prepares the uterus to host a fertilized egg. The follicle from which the egg is known as the corpus lutem. The corpus lutem produces the hormone progesterone in order to prepare the uterine lining (which has developed throughout the menstrual cycle) to become receptive to implantation. If the egg is not fertilized, it will dissolve in the uterus, and uterine lining will be lost during menstruation. If this takes place, the menstrual cycle then will begin all over again.