Excretion In Humans Excretion is one of the essential life processes which is required for a living organism to survive. Excretion is defined as the process of removal of toxic waste materials from one's body.In humans,the nitrogenous waste products,i.e, urea ,is excreted through a well established system called urinary system or excretory system. Human Excretory System consists of a pair of Kidneys and ureters,a Urinary bladder ,and Urethra.Waste is filtered from the blood and is collected in the form of urine in each Kidney. Urine leaves the kidneys through the ureters and is temporarily stored in the Urinary Bladder. From here the urine leaves the body through urethra. Components of Urinary System and their Functions The human Urinary system has following main components- Kidneys Nephrons and Nephric tubules Collecting Tubules Ureters Urinary Bladder Urethra [If you want to read about MECHANISM of urine formation then click here:: Mechanism