The male reproductive system makes millions of sperm and delivers them; the female system releases an egg cell, provides a place for fertilisation and then shelters the developing embryo. This lesson names each organ and its job, compares sperm and egg cells, and follows the zygote through its first week.
Fertilisation is the fusion of the nuclei from a male gamete (sperm) and a female gamete (egg cell); in humans it happens in the oviduct. Sperm are small, numerous and swim using a flagellum; egg cells are large, few and cannot move by themselves. In early development the zygote forms an embryo, which is a ball of cells that implants into the lining of the uterus.
The lab shows diagrammatic models of both systems. Choose female or male, then click each part or pick it from the list to read its function.
| Male part | Function |
|---|---|
| Testes | produce sperm (male gametes) and the hormone testosterone |
| Scrotum | sac that holds the testes outside the body, where it is slightly cooler, which is better for sperm production |
| Sperm ducts | carry sperm from the testes to the urethra |
| Prostate gland | adds fluid to the sperm to make semen; the fluid provides nutrients and allows the sperm to swim |
| Urethra | carries semen (or, at other times, urine) out through the penis |
| Penis | becomes erect to deposit semen in the vagina during sexual intercourse |
| Female part | Function |
|---|---|
| Ovaries | produce egg cells (female gametes) and the hormone oestrogen |
| Oviducts | carry the egg from the ovary to the uterus; fertilisation happens here |
| Uterus | where the embryo implants and the fetus develops; has a thick lining |
| Cervix | ring of muscle at the base of the uterus; it widens during birth |
| Vagina | receives the penis during intercourse, where semen is deposited; also the birth canal |
The sperm duct carries sperm; the urethra carries semen and urine out of the body. The oviduct (not the uterus) is where fertilisation normally happens. The bladder in the model is not part of the reproductive system.
Open the gametes tab. The sperm and egg cell are shown at the same scale, with their key features labelled. Press Release sperm to watch the features at work.
| Sperm | Egg cell | |
|---|---|---|
| Size | very small (head about 5 μm) | large (about 0.1 mm) |
| Structure | head with acrosome and nucleus, midpiece, flagellum | cytoplasm with energy stores, nucleus, jelly coat |
| Motility | swims using its flagellum | cannot move by itself; moved along the oviduct |
| Numbers | millions released at a time | usually one released a month |
Mitochondria give the sperm energy for swimming; they do not make it swim. The flagellum is what moves. Say "release energy by respiration", never "produce energy".
Four quick checks. Each correct answer earns XP and records this skill on your profile.
In the reproductive systems tab, what is the function of the prostate gland?
According to the gametes tab, what does the acrosome contain?
In the implantation tab, where is the zygote when it first starts dividing?
What is the embryo when it reaches the uterus, according to the sim?
Drag the day slider from 0 to 7, or press Play. Follow the where and cells readings as the egg is released, fertilised and carried to the uterus.
The embryo does not implant in the oviduct or the ovary. It implants in the lining of the uterus.
Unlocks once the four checks above are done. Worth more XP, written to IGCSE Paper 2 and Paper 4 standard.
Which structure carries sperm from the testes to the urethra?
Which correctly compares a sperm with an egg cell?
Why does a sperm cell contain many mitochondria?
What is the function of the change in the jelly coat at fertilisation?
This skill is now recorded on your profile. Keep the chain going.