The urinary system produces urine (nitrogenous water) and serves to excrete it to outside the body. Lymphatic system serves in fluid balance, fat absorption and defense. The circulatory system serves in exchange of nutrients and oxygen for waste and carbon dioxide respectively. Respiratory system serves to allow entry of oxygen from the air into blood and exit of carbon dioxide from blood to the air. The integumentary system covers the entire surface of the human body and serves as a barrier, site for waste elimination and temperature control.