Animals accumulate various nitrogenous wastes, including ammonia, urea, and uric acid, due to metabolic processes. The excretory system plays a crucial role in eliminating these wastes and maintaining homeostasis, particularly in humans where the kidneys filter blood to produce urine through three main processes: filtration, reabsorption, and secretion. Different structures, including nephrons and various excretory organs, are vital in this process along with hormonal regulation.