The Respiratory System
Your lungs are in your chest, and they are so large that they take up most of the space in there. You have two lungs, but they aren't the same size the way your eyes or nostrils are. Instead, the lung on the left side of your body is a bit smaller than the lung on the right. This extra space on the left leaves room for your heart.
Your lungs are protected by yourrib cage, which is made up of 12 sets of ribs. These ribs are connected to your spine in your back and go around your lungs to keep them safe. Beneath the lungs is the diaphragm, a dome-shaped muscle that works with your lungs to allow you to inhale (breathe in) and exhale (breathe out) air.
You can't see your lungs, but it's easy to feel them in action: Put your hands on your chest and breathe invery deeply. You will feel your chest getting slightly bigger. Now breathe out the air, and feel your chest return to its regular size. You've just felt the power of your lungs.
• A Look inside the Lungs
From the outside, lungs are pink and a bit squishy, like a sponge. But the inside contains the real lowdown on the lungs! At the bottom of the trachea, or windpipe, there are two largetubes. These tubes are called the main stem bronchi, and one heads left into the left lung, while the other heads right into the right lung.
Each main stem bronchus— the name for just one of the bronchi — then branches off into tubes, or bronchi that get smaller and even smaller still, like branches on a big tree. The tiniest tubes are called bronchioles and there are about 30,000 of them in eachlung. Each bronchiole is about the same thickness as a hair.
At the end of each bronchiole is a special area that leads into clumps of teeny tiny air sacs called alveoli there are about 600 million alveoli in your lungs and if you stretched them out, they would cover an entire tennis court. Now that's a load of alveoli! Each alveolus— what we call just one of the alveoli — has a mesh-like coveringof very small blood vessels called capillaries These capillaries are so tiny that the cells in your blood need to line up single file just to march through them.
• All About Inhaling
When you're walking your dog, cleaning your room, or spiking volleyball, you probably don't think about inhaling (breathing in) — you've got other things on your mind! But every time you inhale air, dozens ofbody parts work together to help get that air in there without you ever thinking about it.
As you breathe in, your diaphragm contracts and flattens out. This allows it to move down, so your lungs have more room to grow larger as they fill up with air. "Move over, diaphragm, I'm filling up!" is what your lungs would say. And the diaphragm isn't the only part that gives your lungs the room theyneed. Your rib muscles also lift the ribs up and outward to give the lungs more space.
At the same time, you inhale air through your mouth and nose, and the air heads down your trachea, or windpipe. On the way down the windpipe, tiny hairs called cilia move gently to keep mucus and dirt out of the lungs. The air then goes through the series of branches in your lungs, through the bronchi and thebronchioles.
• Thank You, Alveoli!
The air finally ends up in the 600 million alveoli. As these millions of alveoli fill up with air, the lungs get bigger. Remember that experiment where you felt your lungs get larger? Well, you were really feeling the power of those awesome alveoli!
It's the alveoli that allow oxygen from the air to pass into your blood. All the cells in the body needoxygen every minute of the day. Oxygen passes through the walls of each alveolus into the tiny capillaries that surround it. The oxygen enters the blood in the tiny capillaries, hitching a ride on red blood cells and traveling through layers of blood vessels to the heart. The heart then sends the oxygenated (filled with oxygen) blood out to all the cells in the body.
• Waiting to Exhale
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