Blood

The blood is a complex organ composed of cells of diverse form that perform diverse functions. Red blood cells or erythrocytes deliver oxygen to the tissues of the body. Platelets govern primary hemostasis, plugging damaged blood vessels after trauma to stop bleeding. The white blood cells (neutrophils, macrophages, eosinophils, basophils, and B- and T-lymphocytes) are all involved in different aspects of immunity from infection. Although most aspects of blood physiology do not change throughout adult life, some disorders of the blood, particularly anemia and neoplastic diseases, do occur more frequently with increasing age.