Humans reproduce sexually, involving a man and a woman. 

The male and female reproductive system have unique functional structures.

For IGCSE Biology, it is important to understand the distinct reproductive systems of male and female.

Male Reproductive System

• Testis (singular): The two testes (plural) produce sperm and testosterone. They are contained in scrotum, which is a bag of skin.
• Sperm duct and glands: The sperm pass through the sperm duct and mix with fluids produced in the glands. The fluid provides nutrients to the sperms. The mixture of the sperm and fluid is called semen.
• Penis: Penis passes urine and semen out from the body. 
• Urethra: Urethra is a tube inside the penis that carries urine and semen. A ring of muscle ensures that urine and semen are not mixed with each other. 

Female Reproductive System

• Ovary: The two ovaries contain ova (female gametes). Every month, an ovum (singular form of ova) develops and matures, and it will be released from one of the ovaries. 
• Oviduct: The oviduct connects the ovaries to the uterus. The oviduct is lined with ciliated cells that help to transport the released ovum to the uterus. Oviduct is where the fertilization of sperm and egg cell happens.
• Uterus: Uterus has a thick and soft lining. It is where a fertilized egg is implanted and develops into a baby until its birth.
• Cervix: Cervix is a ring of muscle at the lower end of the uterus to ensure that the baby stays in place during pregnancy.
• Vagina: The vagina is a muscular tube that leads from the cervix to the outside of the body. 

From Fertilization to Fetus

• During sexual intercourse, a man's penis enters a woman's vagina, and semen is ejaculated into the woman's vagina.
• Sperm cells travel up the vagina, cervix, uterus and oviduct.
• When the nucleus of a sperm cell fuses with a nucleus of an ovum that was released from the ovary, this is called fertilization.
• The fertilized egg is now called the zygote.
• The zygote begins to divide, and the newly originated mass of cells is called the embryo.
• The embryo implants in the walls of the uterus.
• The embryo then develops into a fetus after about 8 weeks.

There are some features that help the fetus to develop:

• Amniotic fluid: Amniotic fluid is fluid in the uterus that surrounds the fetus and supports the fetus. It acts as a cushion for any rough movement, maintains constant temperature and provides an antibacterial environment.
• Placenta: The placenta is connected to the fetus by an umbilical cord. The placenta allows the diffusion of nutrients and oxygen from the mother's blood to the fetus' blood and the diffusion of wastes and carbon dioxide from the fetus' blood to the mother's blood.

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