Explain the sequence of events in the fertiization process in human.

Explanation

Fertilization is a process in which a haploid male gamete fuses with a haploid ovum to form a diploid zygote. The sperms are deposited in the female reproductive tract by copulation and sperms undergo a process called capacitation. It is a biochemical event that enables the sperm to penetrate through the egg membrane and fertilize the egg. Fertilization of ovum takes place only if the ovum and sperm are deposited simultaneously to the ampullary isthmic junction of the fallopian tube. The sperm has to penetrate the multiple layers of granulosa, which are around the ovum forming corona radiata. The follicular cells are held together by hyaluronic acid, an adhesive substance. The acrosome of the sperm secretes a proteolytic enzyme, hyaluronidase, which lysis the membrane and helps the penetration of sperm through corona radiata and zona pellucida. The process is called acrosomal reaction. Once fertilization is over, a barrier membrane, the fertilization membrane around the ovum is formed by the cortical granules from the cytoplasm of the ovum. This membrane prevents further entry of other sperms. Thus polyspermy is prevented.