32 Your Hardworking Heart-Mid

Your Hardworking Heart FOCUS Question How does the human heart work?

你勤奋的心焦点问题人类的心脏是如何工作的?

A Mighty Muscle What's the most important muscle in your body? It's your heart! That's right—your heart is a muscle, and it has a very important job. It pumps blood throughout your body. Most other muscles in your body get to rest now and then, but your heart never stops. It started working long before you were born. It will keep working nonstop for your whole life, without you even thinking about it. Amazing. The heart, blood and blood vessels together make up the circulatory system. That's because the heart causes blood to travel, or circulate, throughout the body. Wowser! Your heart beats about 100,000 times each day. including while you sleep.

你身体上最重要的肌肉是什么? 是你的心脏!没错——心脏是一种肌肉，它有一个非常重要的工作。 它将血液输送到你的全身。 你身体里的大多数肌肉都时不时地休息一下，但你的心脏从来不会停止。 早在你出生前，它就开始起作用了。 它会在你的一生中不停地工作，甚至你都没有想过。 很神奇的。心脏、血液和血管共同构成循环系统。 这是因为心脏促使血液在全身循环。 老古板!你的心脏每天跳动大约10万次。 包括睡觉的时候。

In and Around the Heart Blood enters and leaves the heart through blood vessels. Arteries carry blood away from the heart, and tiny capillaries take it to individual cells. Veins bring blood back to the heart. The heart has four sections, or chambers, that fill with blood at different times. The top two chambers, called atriums, receive blood coming back from the body and lungs. The bottom two chambers, called ventricles, pump the blood out to the body and lungs. The septum is a thick wall of muscle. It separates the left. and right sides of the heart.

心脏内部和周围血液通过血管进入和离开心脏。 动脉将血液从心脏带走，微小的毛细血管将血液输送到单个细胞。 静脉把血液带回心脏。 心脏有四个部分，或心室，在不同的时间充满血液。 最上面的两个腔被称为心房，接收来自身体和肺部的血液。 底部的两个腔室，称为心室，将血液泵出身体和肺部。 鼻中隔是一层厚厚的肌肉壁。 它把左边分开。还有心脏的右边。

One Heartbeat Like other muscles, your heart produces force and motion. It does this by contracting (tightening) and relaxing over and over. When a chamber of the heart relaxes, it fills with blood. When it contracts, it squeezes and pushes the blood out. A single heartbeat 1 The right atrium relaxes and fills with blood from all parts of the body. The left atrium also relaxes and fills with blood from the lungs. 2 The right and left atriums contract and force blood into the ventricles. 3 The right ventricle contracts and pushes blood to the lungs. The left ventricle also contracts and sends blood out to all parts of the body.

和其他肌肉一样，心脏也能产生力量和运动。 它通过反复收缩(收紧)和放松来做到这一点。 当心脏的一个腔室放松时，它就充满了血液。 当它收缩时，它挤压并将血液挤出。 一次心跳右心房放松，身体各部分的血液充满。 左心房也放松并充满肺部的血液。 2左右心房收缩，迫使血液进入心室。 右心室收缩并将血液推向肺部。 左心室也收缩并将血液输送到身体的各个部位。

The four heart chambers work together to keep blood moving through your body all the time. Blood rushes into the atriums and is immediately sent to the ventricles. As the ventricles pump blood out, other blood flows into the atriums. This cycle continues, causing heartbeat after heartbeat. You can actually feel your heartbeat in certain places where blood flows close to the skin. This is called checking your pulse. An average pulse for humans is about 70 beats per minute. Math Moment People often check their pulse for only 15 seconds. then multiply by 4 to figure the beats per minute. Jane counted 16 beats in 15 seconds, and Doug counted 18 beats. What is the difference between their total beats in one minute?

这四个心室一起工作，以保持血液在你的身体一直流动。 血液冲进心房，立即被输送到心室。 当心室泵出血液时，其他血液流入心房。 这样循环不断，导致一次又一次的心跳。 你可以在血液靠近皮肤的某些地方感觉到心跳。 这叫做检查脉搏。 人类的平均脉搏约为每分钟70次。 人们检查脉搏的时间通常只有15秒。 然后乘以4计算出每分钟的节拍。 简在15秒内数了16下，道格数了18下。 他们在一分钟内的总节拍有什么不同?

Which Way? Your heart is a busy place, like a big city where many freeways meet. How does the blood know which way to go? Four valves inside the heart act like security gates. They keep blood moving in the right direction. Two valves direct blood from the atriums to the ventricles. Two other valves direct blood as it leaves the ventricles. All the valves close after blood moves through them to prevent backward flow.

哪条路?你的心是一个繁忙的地方，就像一个有许多高速公路交汇的大城市。 血液怎么知道该往哪边走? 心脏里的四个瓣膜就像安全门一样。 它们使血液流向正确的方向。 两个瓣膜将血液从心房引导到心室。 另外两个瓣膜在血液离开心室时引导血液。 所有的瓣膜在血液通过后关闭，以防止血液回流。