← 🫀 Human body · usually met in Std 6-10
A pair of organs built to put a very large surface in contact with the air, inside a chest that works as a bellows.
Air travels down the trachea, branches into bronchi and then into finer and finer tubes, ending in millions of tiny sacs called alveoli. Each is wrapped in capillaries, and across that thin shared wall oxygen moves into the blood and carbon dioxide moves out. All that branching exists to create surface area: unfolded, the alveoli of one person would cover a sizeable room.
Breathing itself is muscle work. The diaphragm flattens and the ribs lift, enlarging the chest, and air flows in because the pressure inside has dropped. Relax, and it flows out again. You cannot usually feel the need for oxygen — the trigger that makes you breathe is rising carbon dioxide, which is why holding your breath becomes uncomfortable long before you are actually short of oxygen.
Want to see it moving? Search YouTube for “The lungs and breathing” ↗ — we send you to the search rather than to one video, because a link to one video eventually rots.
This entry was written for Star Student in our own words — it is a summary, not a source. Here is where the people who actually hold these facts keep them. Go and check.
Your own textbook ↗Balbharati publishes the textbooks free to read online. Your chapter is the thing to check first — an encyclopedia is a summary, and the syllabus is the syllabus. World Health Organization ↗Health facts stated carefully, and updated when the evidence changes.Last gone through: 1 October 2026 · How these entries are written
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