The Circulatory System
The heart pumps blood around the body.
About this topic
The circulatory system transports oxygen, nutrients, hormones and waste around the body. It is a double circulation: the pulmonary circuit takes blood from the heart to the lungs and back, and the systemic circuit supplies the body. Arteries carry blood away from the heart, veins return it, and capillaries allow exchange.
Arteries have thick elastic walls for high pressure; veins have valves to prevent backflow; capillaries are one cell thick. It supports respiration, and defends and regulates temperature.
Blood in the right side travels to the lungs to pick up oxygen and then returns to the left side, from where it goes around the body. This double circulation lets the blood pressure be boosted after the lungs, so tissues get fast delivery. Arteries carry blood away from the heart in thick, elastic walls, veins return it with valves to stop backflow, and capillaries one cell thick allow exchange.
Lymph vessels collect fluid leaking from capillaries and return it to the blood. Circulation takes about a minute for blood to complete a full loop. A common misconception is that arteries always carry oxygenated blood; the pulmonary artery carries deoxygenated blood. A better rule is that arteries go away from the heart. Heart disease arises when fatty deposits narrow arteries.
Key ideas
- Arteries carry blood away, veins return it
- Capillaries exchange materials
- Double circulation
Quick check
Use cases: where The Circulatory System helps
- Homework: review the key idea behind The Circulatory System before you start a problem set.
- Exam revision: use the quick check to test whether you can recall The Circulatory System without notes.
- Visual learning: play with the interactive lab to see how The Circulatory System changes when you adjust its inputs.
- Teaching a friend: explain The Circulatory System in your own words, then compare your version with the key ideas.
Biology underpins medicine, farming, conservation and biotechnology.
Frequently asked questions
What is The Circulatory System?
The heart pumps blood around the body.
What will I learn in The Circulatory System?
Arteries carry blood away, veins return it. Capillaries exchange materials. Double circulation.
Is The Circulatory System part of Biology?
Yes. It is one of 150 Biology topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the The Circulatory System lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study The Circulatory System?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.