英语听力文摘 English Digest 684 心脏的正确位置你知道么（打印版）

On today’s Moment of Science, we’re sure your heart’s in the right place. But where is it exactly?!? CPR classes show how to press on the sternum, in the center of the chest, to stimulate the heart. But then again, hearing the heartbeat is easier on the left.

Anatomically speaking, the heart is pretty much centered in the chest cavity, although it is tilted to the left, and takes a bit more space from the neighboring left lung than the right.

To understand why the heartbeat’s easier to hear on the left side, we need to know about the four chambers of the heart.

The atria are the two small chambers at the top of the heart. The two ventricles are the larger, more muscular chambers on the bottom. Because the atria simply pump blood down to the ventricles, they don’t need to be that muscular.

The right ventricle needs to be more bulky, because it pumps blood out to the lungs to get oxygen. But the left ventricle has the most difficult task–pumping blood to the rest of the body–so it’s the most muscular chamber of the heart. It’s also closest to the chest wall, while the atria are farther back, tucked under the lungs.

That means that the left ventricle, the hardest-working chamber of the heart, is not only farthest to the left but also closest to the chest wall. And that’s why it’s so easy to hear your heartbeat on the left, even though the heart is nearly centered in the chest.

你确定你的心在正确的地方吗？

在今天的科学时刻，我们确信你的心在正确的位置。但它到底在哪里？！？心肺复苏课程展示了如何按压胸部中央的胸骨，以刺激心脏。但话说回来，听到心跳在左边更容易。

有什么好处？

从解剖学上讲，心脏基本上位于胸腔的中心，尽管它向左倾斜，并且与相邻的左肺相比，右肺占用的空间稍大。

为了理解为什么心跳在左侧更容易听到，我们需要了解心脏的四个腔室。

心之巅

心房是心脏顶部的两个小腔室。两个心室是底部更大、肌肉更发达的心室。因为心房只是将血液输送到心室，所以它们不需要那么肌肉发达。

右心室需要更大，因为它将血液输送到肺部以获取氧气。但是左心室有最困难的任务——将血液输送到身体的其他部位——所以它是心脏中肌肉最发达的心室。它也离胸壁最近，而心房更靠后，藏在肺部下面。

用心工作

这意味着左心室，心脏最坚硬的工作腔，不仅离左边最远，而且离胸壁最近。这就是为什么在左侧很容易听到心跳的原因，即使心脏几乎位于胸部中央。

英语听力文摘 English Digest 684 心脏的正确位置你知道么（在线收听）