The reproductive cycle of female primates is called the menstrual cycle. Menstrual cycle starts only after attaining sexual maturation (puberty). Generally, during ovu lation only one ovum is released per menstrual cycle. The cyclical changes in the ovary and the uterus during menstrual cycle are induced by changes in the levels of pituitary and ovarian hormones. After coitus, sperms are transported to the junction of the isthmus and ampulla, where the sperm fertilises the ovum leading to formation of a diploid zygote.