You don't suck in air, air fills you without trying. It's your rejection of air that forces it back in. Air wants to be full of itself and still. Exhaling takes more energy than inhaling. Nobody yawns enthusiastically, it's always a lazy inhale. The heart is interesting. It is electrical, and the iron in your blood, and the copper in your bone marrow, are separated by your bones as a dielectric barrier. As the iron rich blood flows past the copper core of your bones, it creates a magnetic field and an amber plasma. Naturally your rib cage and heart are the strongest magnetic field source of your body. Flow and glow is the function of the heart, aside from providing oxygen to your cells.