Hematology is a medical specialty devoted to the study of blood and its disorders. Diseases of the blood, by virtue of its generalized nature, spreads throughout the body and its many functions, mainly by transport, and can have serious consequences on the immune system, the oxygenation and the supply of nutrients to the organs, and blood clotting. Blood diseases may come from a disorder of the principal place of production of blood cells, the bone marrow, or a disease directly affecting the blood cells. Among the hematological diseases, are particularly leukemias, lymphomas, and bleeding disorders. Hematology also includes laboratory analyses performed on blood samples studying the constitution of the blood in its various cells and clotting factors.