Fertilization in humans

Fertilization in humans

• Internal Fertilization takes place in humans. That is the fusion of male and female gametes is inside the female body. 
• Millions of sperms are released into the vagina through the penis. 
• Since sperms are motile structures, they travel through the cervix and uterus and reach the ovum or egg cell which is the female gamete in the oviduct.

Only one sperm fuses with the ovum to form a zygote .

Embryo Development

• After the zygote is formed, it undergoes repeated cell division to form an embryo . 
• This embryo is embedded in the thick lining of the uterus and the process is known as implantation . The further the embryo to form the fetus takes place in the uterus itself. 
• After implantation, development of a disc shaped tissue takes place. This is known as placenta . The function of placenta includes: The exchange of food, oxygen and waste materials between the mother and the growing embryo.

Note: The placenta has villi (finger-like projections) which increase the surface area for exchange of materials between the mother and the developing embryo.