1Two gametes join
Humans reproduce sexually. A sperm cell and an egg cell are gametes (sex cells), one from each biological parent. When their nuclei join at fertilisation, the fertilised egg can grow into a baby.
gametespermeggfertilisation
Lesson 10.1 notes
The human reproductive systems
Meet the sperm and egg cells, and follow them through the male and female reproductive systems.
2The sperm cell
A sperm cell is tiny. Its head holds the nucleus, with genetic information from the biological father. The middle is packed with mitochondria that release energy, and the tail lashes to swim.
nucleusmitochondriatail
3The egg cell
The egg cell is one of the biggest cells in the body, about 0.1 mm across. Its nucleus holds genetic information from the biological mother; its cytoplasm has a food store for the embryo.
egg cellfood store
4The male reproductive system
The two testes make sperm. They hang outside the body in a bag of skin, the scrotum. Sperm ducts carry the sperm to the urethra, a tube that runs through the penis.
testisscrotumsperm ducturethrapenis
5Making semen
As the sperm pass, glands add a fluid that feeds them and helps them swim. Sperm and fluid together are semen. The urethra carries semen out, and urine too, but never both at once.
glandssemen
6The female reproductive system
The two ovaries hold egg cells. An oviduct joins each ovary to the uterus (womb), where a baby can grow. The cervix, a ring of muscle, opens into the vagina.
ovaryoviductuteruscervixvagina
7An egg's journey
From puberty, an ovary releases an egg about once a month. Tiny hairs called cilia sweep it along the oviduct towards the uterus. If it meets a sperm there, it can be fertilised.
cilia
Explore: Route finder
Follow a sperm cell or an egg cell through its reproductive system. Stop at each part to see what it does.
Common mistake: Semen is more than sperm
Sperm are cells made in the testes. As they pass, glands add a fluid: sperm and fluid together make semen. One release of semen carries millions of sperm.
Remember
- Sexual reproduction: a sperm cell (the male gamete) and an egg cell (the female gamete) join at fertilisation.
- Male: testes make sperm → sperm ducts → glands add fluid to make semen → urethra → out through the penis.
- Female: from puberty, an ovary releases an egg about once a month → oviduct → uterus, where a baby can develop.
Going further at GCSE
GCSE: Sexual and asexual reproduction → GCSE: Specialised cells →