When you inhale you suck in oxygen ,nitrogen, and other gasses. The way you oxygenate your body is by giving blood the oxygen you need through breathing air into your lungs. The bronchi are tubes that go to each lung and help carry oxygen into your body. The alveoli are little sacks that hold air. The alveoli are covered in blood vessels called capillaries, which absorb oxygen to the blood. You have about 3 million alveoli in your body. The diaphragm is one big muscle that contracts to pull air into your lungs. It’s a dome shape when you breath in. When you exhale the diaphragm flattens. When you exhale you breath out 16% oxygen, 78% nitrogen, and other gasses like carbon dioxide.