Hidden throughout your body are dangerous poisons that must be removed in order for it to survive. The process of excretion involves finding and removing waste materials produced by the body. The primary organs of excretion are the lungs, kidneys, and skin. Waste gases are carried by blood traveling through the veins to the lungs where respiration takes place. Dead cells and sweat are removed from the body through the skin which is part of the integumentary system .
Liquid waste is removed from the body through the kidneys.
During circulation, blood passes through the kidneys in order to deposit used and unwanted water, minerals, and a nitrogen-rich molecule called urea. The kidneys filter the wastes from the blood, forming a liquid called urine. The kidneys funnel the urine into the bladder along two separate tubes called ureters. The bladder stores the urine until muscular contractions force the urine out of the body through the urethra. Each day, your kidneys produce about 1.5 liters of urine.