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Level5-Unit3-Part2-Listening

The Circulatory Syestem1
A flowchart like this one shows how a process begins and ends,end the steps in between.
The process can be of almost any kind from menufacturing(制造业) a tire(轮胎) to creating an advertisement.
Therefore,learning how to describe and explain a process in English is important.
It's important for teachers,engineers and people who provide customer support.




One process that we are all familiar with is our body's circulatory(循环系统) system.
This system provides oxygen throughout the body and eliminates(消除) carbon dioxide which is a waste product.
If something goes wrong with this system,we need to repair quickly or we die.
So it's important to understand it and keep it functioning properly(运作正常).
(It's important to keep it functioning properly or we will die.)




First,the most important requirement for the system to work is a supply of air.
Without fresh air with sufficient(足够充足) oxygen the process won't keep us healthy in alive.
So the process begins by breathing in air,which happens when the lungs(肺) expand and draw in the air.
Once inside the lungs oxygen in the air is exchanging for carbon dioxide in the blood.
This exchange happens when blood cells release(释放放出发布) carbon dioxide and absorb oxygen.
This blood is now oxygenated blood which means it carries oxygen.
(After exchanging CO2 fox oxygen,oxygenated blood flows to the heart.
From the heart it is pumped to the rest of the body.
The carbon dioxide which was exchanged for oxygen is breathed out.
This happens when the lungs contract.)




To summarize,the process begins by inhaling air and oxygenating the blood.
The oxygenated blood in the lungs then flows back to the heart.
The CO2 which came from blood is exhaled(呼出发散) and the next cycle begins.




Note that the blood in the lungs flows in a loop from the heart.
The blood whichenters the loop from the heart carries carbon dioxide.
Once the carbon dioxide is exchanging for oxygen the blood continues through the loop and exists into the heart.
The oxygenated blood is then pumped to the rest of the blood.
(To stay healthy and alive we need fresh air with sufficient oxygen .)




The Circulatory system2
As you can see everthing depends on the flow of blood to and from the heart.
So how does the heart do this?
First the heart which is a muscle has four chabmers.
From one chamber blood is pumped to the lungs.
This is the blood that carries carbon dioxide.
When the oxygenated blood from lungs comes back to the heart it enters another chamber.
This chamber is called the left atrium(中庭).




From the left atrium the oxygenated blood is pumped into another chamber the left ventricle(心房，心室).
The lfet ventrical then pumps the blood into the aorta(大中庭) which is largest artery in the body.
From the aorta the oxygenated blood passes through a network of smaller arteries throughout the entire body including the brain.
Blood returns to the heart through a system of veins(纹) and enters the upper right chamber the right atrium.




Now that we understand a little about the circulatory system we can ask what it needs to operate.
Of course it can't operate without energy.
This energy is supplied by another system,the digestive system which gets energy from food.
And of course,these systems needed to be supported and controlled .
【Level5-Unit3-Part2-Listening】Our skeletal(骨骼) system provides support and our muscular system provides control and movement.
Without support and movement we couldn't get the food that we need for energy.
Only plants can do this,because they have a completely different system which gets energy directly from the sun.




To summarize,the human body is like a huge complex(复杂) factory.
The language we use to describe how it functions is the same language we use to describe almost any industrial(产业) process.
The vocabulary(词汇) is different but the processes flows and logical relationship are almost identical(相同).
Think of some familiar processes in your life or job and see if you can describe and explain it in English.
(Plants get energy directly from the sun by using photosynthesis(光合作用)
Our bodies function very much like a huge complex factory.
From one chamber blood is pumped to the lungs).

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