Functions of the Human Urinary System

Bernadeta T Galea

Sto. Rosario Elementary School

Pateros District

Each part of the urinary system performs important functions - both for the efficient operation of the urinary system itself, and also therefore, for the body as a whole.

Functions of the Kidneys:•Regulation of blood

volume:The kidneys conserve or eliminate water from the blood, which regulates the volume of blood in the body.

• Regulation of blood pressure:The kidneys regulate blood pressure in 3 ways, by:-–Adjusting the volume of blood in the body

(by regulating the quantity of water in the blood - see above),

–Adjusting the flow of blood both into, and out of, the kidneys, and

–Via the action of the enzyme renin. The kidneys secret renin, which activates the angiotensin-aldosterone pathway

• Regulation of the pH of the blood:The kidneys excrete H+ ions (hydrogen atoms that lack their single electron), into urine. At the same time, the kidneys also conserve bicarbonate ions (HCO3

-), which are an important buffer of H+.

• Regulation of the ionic composition of blood:The kidneys also regulate the quantties in the blood of the ions (charged particles) of several important substances.Important examples of the ions whose quantities in the blood are regulated by the kidneys include sodium ions (Na+), potassium ions (K+), calcium ions (Ca2+), chloride ions (Cl-), and phosphate ions (HPO4

2

• Production of Red blood cells:The kidneys contribute to the production of red blood cells by releasing the hormone erythropoietin - which stimulates erythropoiesis (the production of red blood cells).

•Synthesis of Vitamin D:The kidneys (as well as the skin and the liver) synthesize calcitrol - which is the active form of vitam

• Excretion of waste products and foreign substances:The kidneys help to excrete waste products and foreign substance from the body by forming urine (for release from the body).Examples of waste products from metabolic reactions within the body include ammonia (from the breakdown of amino acids), bilirubin (from the breakdown of haemoglobin), and creatinine (from the breakdown of creatine phosphate in muscle fibres). Examples of foreign substances that may also be exceted in urine include pharmaceutical drugs andenvironmental toxins.