Fertilisation:

The process of fusion of a sperm with an ovum is called fertilisation.

• During copulation, semen is released by the penis into the vagina by a process called insemination.
• The motile sperms swim rapidly, pass through the cervix, enter into the uterus and finally reach the ampullary region of the fallopian tube. The ovum released by the ovary is also transported to the ampullary region where fertilisation takes place.
• Fertilisation can only occur if the ovum and sperms are transported simultaneously to the ampullary region.
• Ovum has four layers, outer cells of corona radiate, central zona pellucida and inner perivitelline spece and the innermost plasma membrane. During fertilisation, a sperm comes in contact with the zona pellucida layer of the ovum and induces changes in the membrane that block the entry of additional sperms.
• Acrosome has some hydrolytic enzymes that hydrolyse the layers of ovum to complete fertilization.
• Finally diploid zygote is formed from the fusion of female egg and male sperm.

Fertilization of sperm with ovum: