(N/A) haemodialysing unit is called an artificial kidney because it performs the same fundamental function as the human kidney,which is the removal of metabolic waste products from the blood.
$1$. In patients with kidney failure,the kidneys are unable to filter nitrogenous wastes like urea from the blood.
$2$. The haemodialysis machine uses a dialysing fluid that has the same osmotic pressure as blood plasma,but lacks nitrogenous wastes.
$3$. Blood from an artery is pumped into the dialyser,where it flows through cellophane tubes surrounded by the dialysing fluid.
$4$. Due to the concentration gradient,nitrogenous wastes diffuse out of the blood into the dialysing fluid.
$5$. The purified blood is then returned to the body through a vein.
Since the machine mimics the filtration process of the kidney,it is referred to as an artificial kidney.