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Urinary system

3-minute read

Your urinary system, also called the renal system or urinary tract, removes waste from your blood in the form of urine. It also helps regulate your blood volume and pressure, and controls the level of chemicals and salts (electrolytes) in your body's cells and blood. 

What is the urinary system?

Your urinary system prevents waste and toxins from building up in your blood. It also:

  • helps regulate your blood pressure
  • maintains your body's water balance
  • helps keep bones strong and healthy
  • controls the levels of chemicals and salts in your blood
  • helps make your body's red blood cells

Your urinary system is made up of: 

  • 2 kidneys – organs that filter blood to make urine
  • the bladder – an organ for storing urine
  • 2 ureters – tubes connecting your kidneys to your bladder
  • the urethra – a tube connecting your bladder to your body's surface

How does the urinary system work?

Your kidneys work non-stop, with all of your blood passing through them every 5 minutes. 

The urine that collects is a mix of waste and excess fluid. It is carried to your bladder to be stored. Muscles in the bladder wall stay relaxed, so it can expand as it fills. Other muscles work like a dam to keep urine in your bladder until you are ready to go to the toilet. Your brain controls your bladder, signalling it when to hold urine and when to empty.

To urinate normally, all parts of your urinary tract must work together in proper order. When you are ready to go to the toilet, your bladder outlet muscles (urethral sphincter and pelvic floor) relax and your bladder wall muscles contract. Urine empties from your bladder through your urethra and exits your body. 

Common conditions related to the urinary tract

Urinary tract infection

Urinary tract infections (UTIs) occur when an infection, usually caused by bacteria, enters the urinary tract. The most common types of UTI include:

  • cystitis, an infection of the bladder lining, and the most common lower urinary tract infection
  • urethritis, an infection of the urethra
  • pyelonephritis, an infection of the upper urinary tract, which is very serious because it may affect the kidneys

You should see your doctor if you have symptoms of a UTI. 

Kidney stones

Kidney stones develop when waste chemicals in your urine form crystals that clump together. The can cause tremendous pain. It is important to see your doctor if you think you might have a kidney stone.

Urinary retention

Urinary retention – being unable to empty your bladder, can be acute or chronic.

If you can’t pass urine even though you feel the need to, and your bladder is full, this is acute urinary retention. If you feel you might be in retention, go to your nearest emergency department.

People with chronic urinary retention can urinate, but do not completely empty the urine from their bladders. This can be a slow-developing and long-lasting medical condition.

Prostate problems

Because a man's urethra passes through his prostate, swelling or enlargement of this gland can affect his ability to pass urine. This is one of the most common signs of possible prostate problems.

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Last reviewed: November 2018

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