The main body part involved in the filtration of blood is the kidney. The kidneys play a critical role in maintaining homeostasis by removing waste products, excess salts, and fluids from the bloodstream through a complex filtration process. This process occurs in structures known as nephrons, which filter blood and produce urine. Additionally, kidneys help regulate electrolyte levels, blood pressure, and acid-base balance. Proper kidney function is essential for overall health, as dysfunctional kidneys can lead to serious health issues, including kidney disease.