The body's delivery network
The heart is a pump pushing blood through pipes to deliver oxygen the lungs pulled from the air, and haul away waste. Circulation and breathing are the body's delivery-and-disposal service, running every second without a break.
Delivering oxygen to every cell
The heart is a double pump. The right side sends oxygen-poor blood to the lungs; the left side pushes oxygen-rich blood to the body. In the lungs, oxygen crosses tiny air sacs (alveoli) into the blood while carbon dioxide leaves — this is gas exchange.
Body → right heart → lungs (pick up O₂) → left heart → body (deliver O₂)
Lab · Follow a red blood cell
- Start a cell in the big toe, low on oxygen.
- Trace it back to the heart, then to the lungs.
- Note where it picks up oxygen and where it drops it off.
What you should see: The cell loads oxygen in the lungs and unloads it in the toe's tissues — the circulatory and respiratory systems working as one loop.