“X bodily fluid is just filtered blood!” buddy I hate to break it to you but ALL of the fluids in your body are filtered blood. Your circulatory system is how water gets around your body. It all comes out of the blood (or lymph, which is just filtered blood).

“Okay but why is it always so chemically roundabout and unnecessarily complicated” well buddy, that’s because your blood is imitation seawater. See? It’s very simple.