Process of Fertilization .
About the tenth day after the beginning of the average woman's regular menstrual period an ovum that has developed in one of her two ovaries is stimulated by hormones and enters a sudden period of growth that continues for three or four days. By the end of the thirteenth or fourth teen day of growth ovum is mature. It is encased in a sac of fluid and floats to the surface of the ovary. The sac ruptures and releases the ovum into the Fallopian tube. Millions of feathery hair in the Fallopian tube sweep around the ovum and gently move it towards the uterus. This release of the ovum from the ovary is called ovulation.