In Progress Lesson 1 of 0 In Progress Pregnancy Copulation Copulation means sexual intercourseSexual arousalIn males the penis becomes erect In females the vagina enlarges and becomes lubricatedCopulationDuring copulation the penis moves inside the vaginaOrgasmCopulation results in a pleasurable feeling called orgasmIn males this results in semen being expelled from the penis (ejaculation) Pregnancy Sperm are released into the female system in a process called insemination. This takes place in the vagina, close to the cervixThe sperm swim towards a chemical released from the egg (chemotaxis)Sperm swim through the cervix, along the endometrium and into the Fallopian tubeEnzymes from the head (acrosome) of the sperm break down the membrane of the eggThe head of the sperm enters the eggA new membrane forms around the egg preventing and more sperm from entering the egg Fertile time Sperm and eggs can survive for 2 daysThe fertile time is between days 12 and 16 of the menstrual cycle when a sperm can fertilize an egg released around day 14 Fertilization Fertilization is the union of the nuclei of the sperm and egg to form a diploid zygoteFertilization occurs in the Fallopian tube It normally takes place on days 14 or 15 of the menstrual cycle