The organ responsible for filtering blood in the human body is the kidneys. There are two kidneys, located on either side of the spine, and they play a crucial role in maintaining homeostasis. Each kidney filters waste products, excess substances, and fluids from the blood, producing urine in the process. The kidneys are also vital in regulating blood pressure, electrolytes, and acid-base balance. Any dysfunction in the kidneys can lead to serious health issues, emphasizing their importance in the body's overall function and the maintenance of internal stability.