Level 5 - Unit 3 - Part 2 Listen

As you can see, everything 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 4 chambers. From one chamber, blood is pumped to the lungs. This is the blood that carries carbon dioxide. When the oxygenated blood from the lungs comes back to the heart, it enters another chamber. This chamber is called the left atrium.
正如你所看到的，所有一切都取决于血液进出心脏的流动。心脏如何做到呢？首先，心脏是一块肌肉，它有4个心室。血液从一个心室被推送到肺里，携带着二氧化碳。当含氧血液从肺回到心脏，它进入另一个心室——左心房。

From the left atrium, the oxygenated blood is pumped into another chamber, the left ventricle. The left ventricle then pumps the blood into the aorta, which is the 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 and enters the upper right chamber, the right atrium.
含氧血液从左心房被推送至另一个心室——左心室。 然后左心室将血液推入主动脉——这是人体最大的动脉。从主动脉开始，含氧血液流经整个身体的小动脉网络，包括大脑。血液通过静脉系统回到心脏，进入右心房。

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 need to be supported and controlled. Our skeletal 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.
现在我们对循环系统有了一些了解，我们可能想知道它需要什么来运转。当然，它不能没有能量。这种能量由另一个系统——消化系统提供，从食物中获取能量。当然，这些系统需要得到支持和控制。我们的骨骼系统提供支持，肌肉系统提供控制和运动。没有支持和运动，我们就不能获得提供能量的食物。只有植物能做到这一点，因为它们有一个完全不同的系统，可以直接从太阳获取能量。

To summarize, the human body is like a huge, complex factory. The language we use to describe how it functions is the same language we use to describe almost any industrial process. The vocabulary is different, but the processes, flows and logical relationships are almost identical. Think of some familiar process in your life or job and see if you can describe and explain it in English.
总而言之，人体就像一座巨大而又复杂的工厂。我们用来描述它如何运作的语言和我们用来描述几乎任何工业过程的语言是一样的，词汇不同，但是过程、流程和逻辑关系几乎是相同的。想几个在你生活或工作中熟悉的过程，看看你是否能用英语描述和解释。