There are certain things we need to do every single day. Some of those things we think about, such as eating and drinking. In fact, if you're hungry, you might be thinking about your next meal right now!

Some of the things we do every day we don't think about at all, though. For example, when's the last time you thought about breathing? Unless you just ran a race or have a bad cold, you probably take breathing for granted and don't give it a second thought. Isn't it interesting how something so critical to life goes on without you even thinking about it?

Breathing is as necessary to life as your heart pumping blood through your body. In fact, the necessity of breathing is closely linked to that blood pumping through your vessels. Your organs responsible for breathing are your lungs, which are part of the respiratory system.

Your lungs sit in your chest, protected by your rib cage. They are large and take up most of the space in your chest cavity, along with your heart. Below your lungs you'll find the diaphragm, which is the large muscle that works with your lungs to help you breathe in (inhale) and out (exhale).

Even though you can't see your lungs, it's very easy to feel them at work. Simply put your hands on your chest and take a few deep breaths. You can feel your chest expand as you inhale and return to its normal size when you exhale.

As you inhale, oxygen in the air travels through your lungs into tiny air sacs called alveoli. The alveoli in your lungs are covered with tiny blood vessels called capillaries. The oxygen you breathe in is transferred to your blood through the capillaries.

All of your body's cells need oxygen. As capillaries in the lungs pick up oxygen, they send the oxygenated blood to the heart, which pumps it out to the rest of the body. When you exercise, your body's cells need even more oxygen. That's why your heart beats faster and you breathe faster when you exercise. Your body ramps up these processes to provide the oxygenated blood that your body's cells need.

Your blood and lungs also help to get rid of waste products your body doesn't need, such as carbon dioxide. The capillaries bring these by-products to the alveoli, where they are then pushed back out through the lungs when you exhale.

So how often does all of this in and out breathing take place? It depends upon your age and activity level. Children tend to have more rapid breathing rates. For example, newborn babies often breathe 30-60 times per minute. Toddlers might breathe 20-30 times per minute. Older children and adults, when resting, usually breathe about 12-20 times per minute. Over the course of a day, that adds up to 17,000-30,000 breaths per day — or more!

Those average breathing rates are for when you're at rest. When you exercise — or even walk around the house or school — your breathing rate goes up. It's quite possible you might breathe 50,000 times or more per day if you're active!

All that breathing keeps the level of oxygen in your blood at the appropriate level for whatever activity you're doing. Doctors sometimes measure the level of oxygen in your blood (called the blood oxygen level) to make sure your lungs are working properly.

The most common way to measure your blood oxygen saturation is with a pulse oximeter. A pulse oximeter uses light to measure the oxygen saturation level by attaching a small sensor to the end of one of your fingers. A normal oxygen saturation level would be somewhere between 95-99%.

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