At the beginning of the process, the sperm undergoes a series of changes, as freshly ejaculated sperm is unable or poorly.
Only about 1 in 1 million sperm that are ejaculated into the vagina will reach the site of fertilization. Estrogen also relaxes the cervix, causes cervical mucus to.
Fertilization occurs when a sperm and an oocyte (egg) combine and their nuclei fuse. Because each of these reproductive cells is a haploid cell containing half.