1. A flow chart, like this one, shows how a process begins and ends, and the steps in between.

2. The process can be of almost any kind, from manufacturing a tire to creating an advertisement.

3. Therefore, learning how to describe and explain a process in English is important.

4. It's important for teachers, engineers, and people who provide customer support.

5.One process that we are all familiar with is our body's circulatory system.

6. This system provides oxygen throughout the body and eliminates carbon dioxide, which is a waste product.

7.If something goes wrong with this system, we need to repair it quickly, or we die.

8.So it's important to understand it and keep it functioning properly.

9. First, the most important requirement for the system to work is a supply of air.

10. Without fresh air with sufficient oxygen, the process won't keep us healthy and alive.

11. So the process begins by breathing in air, which happens when the lungs expand and draw in air.

12.Once inside the lungs, oxygen in the air is exchanged for carbon dioxide in the blood.

13. This exchange happens when blood cells release carbon dioxide and absorb oxygen.

14.This blood is now oxygenated blood, which means it carries oxygen.

15. To summarize, the process begins by inhaling air and oxygenating the blood.

16. The oxygenated blood in the lungs then flows back to the heart.

17. The C02 which came from the blood is exhaled, and the next cycle begins.

18.Note that the blood in the lungs flows in a loop from the heart.

19. The blood which enters the loop from the heart carries carbon dioxide.

20.Once the carbon dioxide is exchanged for oxygen, the blood continues through the loop and exits into the heart.

21. The oxygenated blood is then pumped to the rest of the body.

Inside the lungs, oxygen is exchanged for carbon dioxide.（前文未见生句）

The system won’t work without a supply of air.（前文未见生句）

From the heart it is pumped to the rest of the body.（前文未见生句）

Our bodies function very much like a huge, complex factory.（前文未见生句）