4. 正常心音 Normal Heart Sounds

未能成功加载,请稍后再试
0/0

翻译:NicoleZ;修饰:匕 莽

If you put a stethoscope over the chest, you'll usually hear something that sounds like lub dub, lub dub, lub dub, which repeats over and over again, with each cardiac cycle, or heartbeat.

Now, the question is, where does this sound come from?

Normally, blood is constantly moving through the four chambers of the heart- coming through the veins into the right atrium, going to the right ventricle, then shooting off via the pulmonary arteries to the lungs and coming back from the pulmonary veins into the left atrium and the left ventricle, to be pumped into the aorta.

So, in every step, some valves have to open and others have to close.

Valves are just "communicating doors" that, when open, allow blood to pass through, and when closed, hold blood within a chamber.

So, in total, our heart has four valves- two atrioventricular valves, which separate the atria from the ventricles and are the mitral valve, on the left side, and the tricuspid valve, on the right side, and two semilunar valves, which separate the ventricles from the large arteries coming off of them and are the pulmonary valve, on the right side, and the aortic valve, on the left side.

And when these valves are closing, just like a door slamming shut, they are going to make a sound that is transmitted in the direction of the blood flow.

Now the heart is positioned in such a way that the sound of the closing of each of these valves is projected onto a small area on the chest wall.

If you place a stethoscope between the second and third rib, known as the right second intercostal space, just next to the upper border of the sternum, you'll hear the aortic valve closing.

Then, if you place a stethoscope in the left second intercostal space, at the left upper sternal border, you can hear the pulmonary valve closing.

下载全新《每日英语听力》客户端,查看完整内容