Respiratory System
Lungs exchange oxygen and carbon dioxide.
About this topic
The respiratory system brings oxygen into the body and removes carbon dioxide. Air passes through the nose, trachea, bronchi and bronchioles to the alveoli, tiny air sacs with thin walls and rich capillary networks, where gas exchange happens by diffusion.
Alveoli are adapted with a large surface area, thin walls, moist lining and good blood supply. Cilia and mucus trap dust and germs. Conditions such as asthma, emphysema and pneumonia affect this system.
You breathe about 12 to 20 times a minute at rest. Alveoli number around 300 million in the lungs, giving a surface area of roughly 70 square metres. They are moist, thin and surrounded by capillaries, ideal for gas exchange by diffusion, with oxygen going into the blood and carbon dioxide coming out. Cilia and mucus in the airways trap dust and microbes.
Smoking damages cilia and the alveoli, causing bronchitis and emphysema and increasing the risk of lung cancer. Asthma narrows the bronchioles during attacks and is treated with inhalers. A common misconception is that the lungs are muscular; they have no muscles and are inflated by the diaphragm and rib muscles. Another is that exhaled air is only carbon dioxide; it still contains about 16 percent oxygen.
Key ideas
- Trachea, bronchi, alveoli
- Diaphragm moves air
- Gas exchange by diffusion
Quick check
Use cases: where Respiratory System helps
- Homework: review the key idea behind Respiratory System before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Respiratory System without notes.
- Visual learning: play with the interactive lab to see how Respiratory System changes when you adjust its inputs.
- Teaching a friend: explain Respiratory System in your own words, then compare your version with the key ideas.
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Frequently asked questions
What is Respiratory System?
Lungs exchange oxygen and carbon dioxide.
What will I learn in Respiratory System?
Trachea, bronchi, alveoli. Diaphragm moves air. Gas exchange by diffusion.
Is Respiratory 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 Respiratory 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 Respiratory 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.