BLOOD from the Latin sanguinem Fluid circulating through the veins, arteries and capillaries of higher animals, consisting of a liquid part, plasma, and a solid part, blood cells and platelets. The function of generation or hematopoiesis is performed by the liver and spinal cord. A human being has between 4, 5 and 6 liters of blood in the body, constituting 7 to 8% of the total weight. Plasma contains water, proteins, mineral salts and vitamins that nourish the organs. The solid part is made up of white blood cells or leukocytes, red blood cells or red blood cells and platelets or thrombocytes. White blood cells, 1% of the blood, are of five types: neutrophils (granulocytes also called polymorphonuclear 60 to 70% of leukocytes), eusinophils (granulocytes that circulate about 6 to 12 hours in the blood and then go to tissues), basophils, monocytes (the largest leukocytes and 2 to 8% of leukocytes, are part of the mononuclear lymphatic system) and lymphocytes. The first 4 types of white blood cells make up the myeloid. Lymphocytes, the fifth type, make up the lymphoid. The lymphoid is, in turn, made up of T lymphocytes or thymocytes, which come from stem cells and attack infections, but are fundamental against cancer; by B lymphocytes, which also come from stem cells and generate antibodies; and by NK (Natural Killer) cells first line of defense against infections and other pathologies. Red blood cells, also called erythrocytes or red blood cells, are responsible for transporting oxygen to different tissues. Hemoglobin is its main component and they are the most abundant blood cells. The blood acquires its intense red color when hemoglobin is loaded with oxygen in the lungs which allows to distinguish the arteries. The veins, on the other hand, carry deoxygenated blood and with carbonic anhydride which makes it bluish-red dark, which is why it is graphed blue. When a person has low oxygen content they see bluish skin (cyanotic) and the pathology is called cyanosis, a name derived from hydrocyanic acid (CHN) which is deep blue). HCN is used to execute death row inmates because it blocks the possibility that red blood cells can acquire oxygen, causing suffocation in a matter of seconds. Platelets or thrombocytes, named for their flattened shape, have the function of clotting blood when cuts or wounds occur. The pathology resulting from non-coagulation in these circumstances is hereditary and is called hemophilia. Leukemia is cancer of blood tissues, including the bone marrow