The urinary system

Blue and red blood vessels.  The blue show blood coming from the kidneys going to the heart. The red show blood going to the kidneys from the heart. Bladder, urethra and kidney are labelled.

Blood is brought to the kidney in the renal artery. The kidneys filter the blood and then reabsorb useful materials such as glucose. After it has been purified, the blood returns to the circulation through the renal vein.

Urine is taken from the kidneys to the bladder by the ureters. The bladder stores the urine until it is convenient to expel it from the body.

Note that ‘ureter’ differs from the word ‘urethra’. The ureters are tubes that carry urine from the kidneys to the bladder, whereas the urethra is the tube that carries urine out of the body.


Urine contains water, urea and salts. Urea is produced in the liver when excess amino acids are broken down. It is the main waste product removed in the urine.