Human reproduction – fertilisation, pregnancy and the placenta
BiologyHuman & Animal PhysiologyAges 16–17
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Labelled diagrams of the female and male reproductive systems with a naming quiz, a timeline from fertilisation in the oviduct through cleavage, blastocyst, implantation, gastrulation and organ formation to birth, with fetal size and the hormones of pregnancy, a placenta screen where you set smoking, alcohol and infection and read the effects on the fetus, and fish, frog, chick and human embryos compared.
Lesson: Human reproduction: fertilisation, pregnancy, the placenta and birth
What it shows
In humans an egg is fertilised by one sperm in the oviduct. The zygote divides into a ball of cells and becomes a blastocyst, which implants in the lining of the uterus about a week later. Its inner cell mass forms the three germ layers and then all the organs, while the trophoblast helps to form the placenta. Across the thin placental barrier oxygen, glucose and antibodies diffuse to the fetus and carbon dioxide and urea pass back; alcohol, nicotine and some pathogens also cross. Birth is driven by oxytocin in a positive feedback loop.
How to use
On Reproductive systems, choose Female or Male, tap a part to read its function, or press Quiz. On Development, press Run or Step, or drag Time after fertilisation; press Record to build a growth table and Label the blastocyst for the labelling task. On Placenta, set Mother smokes, Alcohol and Infection of the mother and compare the birth mass.
Parameters you can change
- Screen Reproductive systems, Development, Placenta, Embryos compared
- System Female, Male
- Time after fertilisation 0–266 days
- Mother smokes 0–20 cigarettes/day
- Alcohol 0–14 units/week
- Placenta surface area 40–100 %
- Infection of the mother None, Rubella (virus), Toxoplasmosis (parasite), Bacterial infection
- Stage Early embryo, Middle, Late
Questions to explore
- Why must the blastocyst implant in the uterus lining before it can keep growing?
- Which adaptations make the placenta efficient at exchanging substances by diffusion?
- Why does the release of oxytocin during birth keep increasing until the baby is born?
