Urinary System

The urinary system consists of the kidneys, ureters, bladder, and the urethra. The kidney consists of millions of functional units called nephrons. The urinary system removes wastes from the body and regulates blood volume and blood pressure. It also controls the levels of electrolytes and metabolites in body fluids and regulates blood pH.

The urinary system maintains homeostasis by regulating water and electrolytes within the body. The kidneys produce urine which consists of water and dissolved metabolic wastes such as nitrogenous compounds (urea and uric acid), excess ions and some drugs.

The urinary system is an important part of the body. Its proper functioning is crucial for maintaining health.

The kidneys perform the following functions:

  • Produce urine which is excreted out of the body (micturition)
  • Maintain water, electrolyte and acid-base balance
  • Secrete erythropoietin, a hormone which stimulates the formation of red blood cells
  • Secrete renin, an important enzyme which controls blood pressure

Urine is produced in the kidneys by filtration of blood. The urine then passes through the ureters to the urinary bladder, where it is stored. During urination, the urine passes from the bladder through the urethra to the outside of the body.

In adult humans about 1-2 litres of urine is produced per day. The amount of urine produced depends on many factors such as the state of hydration, activity level, environmental factors, weight, and the individual’s health.

Topics in this Section

The Kidneys
  • Kidneys
    • Organs associated with the kidneys
    • Gross structure of the kidney
    • Microscopic structure of the kidney
    • Functions of the kidney
  • Ureters
    • Structure
    • Function
  • Urinary bladder
    • Organs associated with the bladder
    • Structure
  • Urethra
  • Micturition
  • Diseases of the kidneys
    • Glomerulonephritis (GN)
    • Nephrotic syndrome
    • Diabetic kidney
    • Hypertension and the kidneys
    • Acute pyelonephritis
    • Chronic pyelonephritis
    • Acute renal failure
    • Chronic renal failure
    • Renal calculi
    • Congenital abnormalities of the kidneys
    • Tumors of the kidney
  • Diseases of the renal pelvis, ureters, bladder and urethra
    • Obstruction of the outflow of urine
    • Infections of the urinary tract
    • Tumors of the bladder
    • Urinary incontinence