IGCSE Biology / Reproduction in humans
The human reproductive systems
Edexcel International GCSE Biology (4BI1), chapter 9: Reproduction in humans, specification point 3.8. Free lesson.
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The human reproductive systems make and transport gametes, which are sperm and eggs. Knowing each structure’s function helps you label the systems and explain where fertilisation and implantation happen.
How the male reproductive system works
Follow the route taken by a sperm cell to remember the main structures. Sperm are made in the testes, and fluid from glands combines with sperm to form semen. Testes make sperm and the sex hormone testosterone. The scrotum holds the testes outside the body. This keeps them a few degrees cooler than core body temperature, which is best for sperm production. Sperm ducts carry sperm from the testes. Glands, including the prostate gland, add fluid to sperm. Sperm and this fluid together make semen. The urethra carries semen through the penis. It also carries urine, but not at…
How the female reproductive system works
Follow the route taken by an egg to remember the main structures. Fertilisation and implantation happen in different places, so be clear about which structure is involved in each. Ovaries make eggs and produce the hormones oestrogen and progesterone. Oviducts, also called fallopian tubes, receive an egg released from an ovary. Fertilisation happens in an oviduct. The uterus has a thick muscular wall. A fertilised egg implants there, and a fetus develops in the uterus. The endometrium is the lining of the uterus. It thickens each cycle and is lost if implantation does not…
How the two systems compare
Both systems make and transport gametes, but they differ in how many gametes are made and which hormones are produced. Fertilisation takes place in the female reproductive system. Gametes are sperm and eggs. Sperm are made in the testes, while eggs are made in the ovaries. Hundreds of millions of sperm are made continuously. About one egg is made every 28 days. The testes produce testosterone. The ovaries produce oestrogen and progesterone. Sperm travel along a sperm duct. An egg travels along an oviduct. Fertilisation happens in the female oviduct, where a sperm and egg can meet.
Where fertilisation and implantation happen
Fertilisation is when a sperm and egg join. Implantation is when a fertilised egg attaches to the uterus lining. These happen in different places and several days apart. Fertilisation happens in the oviduct. Implantation happens in the endometrium, the lining of the uterus. Remember the key locations: testes make sperm, ovaries make eggs, fertilisation happens in the oviduct, and implantation happens in the uterus lining.