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 (say: tray-kee-uh), or windpipe, there are two large tubes. These tubes are called the main stem bronchi (say: bron-keye), and one heads left into the left lung, while the other heads right into the right lung. Each main stem bronchus (say: bron-kuss) - 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 (say: bron-kee-oles), and there are about 30,000 of them in each lung. 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 (say: al-vee-oh-lie). 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 (say: al-vee-oh-luss) - the name for one of the alveoli - has a mesh-like covering of very small blood vessels called capillaries (say: cap-ill-er-ees). 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 a 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 of body 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 they need. 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 or nose, and the air heads down your trachea, or windpipe. On the way down the windpipe, tiny hairs called cilia (say: sill-ee-uh) 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 the bronchioles. 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 need oxygen 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 veseels to the heart. The heart then sends the oxygenated (filled with oxygen) blood out to all the cells in the body.