- Cell metabolism (chemical reactions happening in the body) leads to the build-up of waste products in the blood, including carbon dioxide and urea.
Carbon dioxide is formed in the energy releasing process of respiration in all living cells.
Urea is formed in the liver from the breakdown of excess amino acids which is removed by the kidneys as urine.
- The urinary system:
The renal artery brings in the blood, containing waste products, to the kidneys. The kidneys filter the blood getting rid of urea and other substances (e.g. excess ions, excess water) forming urine, then sends the clean blood out of the kidneys and back to the body via the renal vein. The waste products (urea) and any excess water (urine) go through the ureters and gets stored in the bladder. The urine flows through the urethra, whenever it’s time for the person to urinate, and exits the body.
- Treatments for kidney failure:
A kidney dialysis machine keeps the patient alive until a transplant is available, it removes waste products from a patient's blood, and it filters the blood mechanically. They are expensive and a patient would have to be connected to it for several hours, several times a week.