Pregnancy: implantation and placenta sim
Drag the day slider to follow the zygote along the oviduct as it divides into a ball of cells and implants in the uterus lining; then drag a probe along a model placenta villus to read oxygen, glucose, carbon dioxide and urea crossing between the mother's and the fetus's blood, and bump the amniotic sac to see the fluid cushion the fetus.
Reproduction in humans: early development, implantation, the placenta and the amniotic sac · covers the O-Level, IGCSE topic
What the sim shows
Early pregnancy: a model. Drag the day slider (days 0 to 10 after fertilisation): the egg is fertilised in the oviduct, and the zygote divides by mitosis into a ball of cells that cilia and muscle move along the oviduct. It reaches the uterus about day 4 and implants in the thick lining from about day 6 to day 10. Then drag the probe along the placenta model. Here the fetus's blood, in a villus, runs beside the mother's blood with a thin barrier between them. Oxygen and glucose diffuse to the fetus, and carbon dioxide and urea to the mother, each down its gradient; blood cells do not cross, so the bloods never mix (IGCSE Supplement: some toxins and pathogens can cross). The amniotic sac model shows the fluid cushioning the fetus. Simplified on purpose: the embryo is drawn 100 times its real size (about 0.1 to 0.2 mm) on an oviduct board about life length (10 cm), so the two are not to the same scale; the days are typical (real timings vary); the placenta model is one villus beside a well-mixed pool of the mother's blood, with levels that are illustrative (≈), and it halves each gap along the villus (oxygen arrives at 2.4 kPa and leaves at 3.9 kPa, against 5.4 kPa in the mother's blood); amino acids, water and antibodies also cross but are not modelled; the bead and blood colours follow real blood (the fetus's blood is darker red where it arrives, short of oxygen), and the bead colours are a key (the substances are colourless); the fetus and sac are not to scale.
- Lit pointer: the day after fertilisation you have chosen
- Close-up: graphs of your readings, and what is happening
- Dashed line: the level in the mother's blood
Use it in your lessons
- Try it here: anyone can unlock 2 figures free, and a free account unlocks up to 5. Runs on a laptop, a Chromebook or a phone; nothing to install.
- Present it and share student links with the teacher plan, from US$5 a month, billed yearly.
- Put it on your own website or LMS for US$9, paid once, or every sim from US$29 a month.
Free guide: 12 practicals as sims, and how to run one in a lesson →
Need a version for your exact set-up? Have one made: US$49 a figure in an order of 5.
More biology sims
- Arteries, veins and capillaries simSlide a stained artery-and-vein section under a microscope to compare the walls, lumens and capillaries at real size, take your own pressure and speed readings along the circuit, and squeeze a vein-valve model to see the valves open and shut.
- Bile and emulsification simAdd bile (or water) to oil, shake and watch the droplets split on a microscope screen, then time lipase turning pink phenolphthalein colourless at 35 °C and plot how the time falls as the surface area grows.
- Blood components and clotting simSteer a stained blood smear under a microscope (×100 to ×1000 with oil) to find and name red cells, phagocytes, lymphocytes, platelets and plasma, then cut a small vessel and step through clotting in the book's order, and read the layers of settled blood.
- Capillary exchange and tissue fluid simPump up the pressure and set the flow on a working capillary model, then watch fluid, oxygen and glucose leave one real capillary and carbon dioxide enter, take your own readings and graph them.
- Coronary heart disease simGrow a fatty plaque in a coronary artery on a heart teaching model with risk-factor sliders, watch blood flow to the heart muscle fall, let a clot cause a heart attack, and drag a catheter to put in a stent.
- Double circulation: follow a red cell simDrag a red bead (one red blood cell) round a classroom double-circulation board through the lungs, heart, liver, gut, kidney or legs, predict each next vessel, read its oxygen saturation and the two pressure gauges, and record and graph the readings.