<P> Only the organs specifically used for the excretion are considered a part of the excretory system . In the narrow sense, the term refer to the urinary system . However, as excretion involves several functions that are only superficially related, it is not usually used in more formal classifications of anatomy or function . </P> <P> As most healthy functioning organs produce metabolic and other wastes, the entire organism depends on the function of the system . Breaking down of one of more of the systems is a serious health condition, for example renal failure . </P> <P> The kidneys are bean - shaped organs which are present on each side of the vertebral column in the abdominal cavity . Humans have two kidneys and each kidney is supplied with blood from the renal artery . The kidneys remove from the blood the nitrogenous wastes such as urea, as well as salts and excess water, and excrete them in the form of urine . This is done with the help of millions of nephrons present in the kidney . The filtrated blood is carried away from the kidneys by the renal vein (or kidney vein). The urine from the kidney is collected by the ureter (or excretory tubes), one from each kidney, and is passed to the urinary bladder . The urinary bladder collects and stores the urine until urination . The urine collected in the bladder is passed into the external environment from the body through an opening called the urethra . </P> <P> The kidney's primary function is the elimination of waste from the bloodstream by production of urine . They perform several homeostatic functions such as: - </P>

What body system works with the excretory system