字幕列表 影片播放 列印英文字幕 Hi there! Can you guess what I am? I'll give you a hint... I have a very important job inside your body and your heart helps me to do my job. I'm a red blood cell! My job is so important that you'll thank me for it later! But I can't take all the credit. Without your heart I couldn't do a thing! You see, I'm like a little delivery truck in your body. I pick up and drop things off all the time. I ride the highways of something called the circulatory system. I like to call it the Circle System because I keep going in circles! This system is made of your heart and blood vessels that carry your blood to different areas of your body. Your blood vessels are like tiny tunnels that run all through your body. They are made up of arteries that take oxygen to places in your body, and veins that take carbon dioxide from your body to your lungs. This is MY highway. But I can't move by myself. I move within your blood when it moves. How does your blood move, you ask? Why, your heart pumps it. Let me show you how. Your heart is the most important muscle in your body. It moves by itself and even though you can hardly feel it, it keeps moving all the time, even when you are sleeping. Want to feel your heart move? Sit very still and put your hand on your chest. If you were running hard or exercising you might find it easier to feel. When your heart moves it's called a "heartbeat". Your heart makes at least 100,000 heartbeats every day. When your heart beats it pulls blood into it and pushes it out again. This helps the blood to move fast enough to go through your whole body and back. And it helps me to pick up my deliveries and take them to different places in your body. I'm not alone in there. There are lots of red blood cells just like me doing the same thing in your body all the time. Even now, while I'm talking to you! Here's me at the start of my little journey. I just got back from dropping off some things to some places in your body. I need to get some more speed to do more deliveries so I ride your bloodstream into your heart. Going through the heart is easy because the heart has special rooms and doors that only open one way. Right now I am entering the right side of the heart. I go through the first room called the "right atrium", through the first door called the "tricuspid valve", and through the second room called the "right ventricle", and through the second door called the pulmonary valve. The heartbeat causes the heart to squeeze the blood in these rooms into the next area. It pushes the blood through it and into the arteries (like tunnels) that lead to other parts of the body. So, now I'm moving a little faster cause the heart has given me a push. Now I need to go and pick up the things I need to deliver. My first stop is to the lungs. I need to pick up a little oxygen molecule to take to someplace in the body. Every body needs oxygen. Our lungs bring it into our body, and then I pick it up and take it to where it's needed. It seems like it would be tricky to pick up the oxygen, but the lungs really help me with that job. You see, here in the body we all work together and co-operate to keep everything running smoothly. When I get to the lungs... (I'm not really this big, it's just easier to see me this way) ... and I get really close to the sides of my little tunnel... ... the oxygen that is sort of floating out of the walls nearby just jumps onto me for the ride. When enough of it has hopped on and I can't hold anymore then I'm ready to go back to the heart for another push. Know what? This all happens so fast that it's even faster than blinking! So now this time I need to go in the other side of the heart. This side is for all of us red blood cells that are carrying oxygen. The heart pushes us a little farther this time because some of us have a very long trip. I go in through the first room called the "left atrium" through the "mitral valve" "doorway" and into the "left ventricle" room to get my big push. Then out I go and on my journey! I like my job because I get to travel. Here I am making a delivery in the foot area! All I have to do is draw near to the tunnel wall and the oxygen will just jump out of my truck and squeeze out of the tunnel! It's pretty neat to watch. While this is happening I also make another pick-up. Carbon dioxide needs to be taken up to the lungs so that the body can get rid of it by breathing out. And I'm just the cell to do it! I grab some and off I go again. Going back up to the heart is a little tricky because I need to ride up. It's kind of like climbing a hill. Because of this the veins have little trap doors called valves that only open one way. This stops me from floating in the wrong direction. So I keep going up and up as the heart keeps beating and pushing the bloodstream along. Eventually I get back to the heart again where I get ready to drop off the carbon dioxide in the lungs and get a good push to get me going on another pick-up. So that's my job! What do you think? Pretty important isn't it? The heart really helps me to do my job well!