B3.1
The uninary system
The urinary system is designed to remove waste products such as urea, as well as excess ions and water from our blood. The kidneys contain many nephrons which remove any waste, before reabsorbing any substances the body needs. Waste is stored in the bladder before being removed as urine.
The urinary system overview
Waste products are produced by our cells. These include carbon dioxide from respiration and urea from the breakdown of excess amino acids in the liver.
Carbon dioxide is removed by our lungs. Our urinary system is responsible for producing, storing and removing urine from our bodies. Our urine contains urea and any excess water.
The kidneys
The kidneys are part of the urinary system, together with the ureter, urethra and bladder. Humans have two kidneys. They are bean-shaped organs - approximately 11.5 cm long – which are found just below our ribcage, one on either side of our spine. location of kidneys in abdominal cavity
The renal arteries take blood with waste products to the kidneys to be filtered. Renal veins then return the filtered blood to be circulated around the body.
Blood vessels take the blood though the kidneys where the waste products are removed into convoluted tubules. These tubules join together to form the ureter, which transports urine to the bladder where it is stored. Urine is then passed from the bladder to the urethra to be released.
Kidney failure
Since the kidney is responsible for the removal of waste from the blood, any damage (either from accidents or disease) can lead to a build-up of poisonous waste products in the body.
We can survive without one kidney very well, but total kidney failure would be fatal if not treated. Treatment can take the form of dialysis on a kidney machine or a kidney transplant.

Kidney dialysis machine
A dialysis machine can keep a patient alive until a