One heart, two connected circuits
The right side pumps blood to the lungs to collect oxygen. The left side pumps it to the body. Blood returns to the heart, completing one continuous journey.
Study each circuit and answer three questions at each teaching stage. Then answer twelve application questions to unlock the next heart lesson. You can revisit completed stages.
The heart has four chambers. The two upper chambers, called atria, receive returning blood. The two lower chambers, called ventricles, pump blood out. Valves act as one-way doors between chambers and at the exits.
An artery carries blood away from the heart; a vein brings it back. These names describe direction, not oxygen content. Capillaries are tiny vessels where blood exchanges substances with the surrounding tissues.
Learning outcomes
- Explain how venous valves prevent backflow and compare capillaries with sinusoids.
- Trace systemic circulation and explain how it connects to pulmonary circulation.
- Relate the structure of arteries, arterioles, capillaries, venules and veins to their functions.
- Explain how the vessel types form a continuous pathway.
- Explain the exchange of gases, nutrients and wastes between blood and tissues.
How to explore
Drag to rotate and scroll to zoom. Click a part to identify it, then choose Read more for its explanation. Labels stay outside the model. Use the keyboard structure list for the same information.