Mammalian blood components. Animation of a chart summarizing the components of mammalian blood. The three main components are the plasma (the liquid component), the cells, and the platelets (also considered a type of blood cell). Platelets (thrombocytes) help stop bleeding. Plasma consists of fibrinogen and serum. Fibrinogen is a glycoprotein that like platelets plays a vital role in blood clotting. Serum consists of the remaining blood proteins, electrolytes, antibodies, antigens, and hormones. The two main types of blood cells are red blood cells (erythrocytes) and white blood cells (leucocytes). Red blood cells are responsible for oxygen transport and the removal of the waste gas carbon dioxide following respiration. White blood cells are part of the immune system and responsible for defense against disease. The white blood cells are here divided into granulocytes (polymorphonuclear leucocytes) and agranulocytes (mononuclear leucocytes). Three granulocytes are shown: eosinophils, neutrophils and basophils. Two agranulocytes are shown: lymphocytes and monocytes.