So far Sally learnt about transport of food, oxygen and water via blood. But she still wasn't clear about how blood acted as a medium for removal of waste materials from the body. She asked the doctor about the same. The doctor said that blood collects the waste material from the tissues and takes it to the ___________ where it is filtered out of the blood capillaries whereas useful materials are retained by the blood.
Wastes excreted from cells get dissolved into the blood. The blood carries them to kidneys where an extensive network of blood capillaries filters the waste material out of the blood while the useful substances and excess water is reabsorbed into the blood.