Blood transports oxygen and nutrients to all parts of the body and carries away carbon dioxide and other waste materials. Oxygen is carried inside red blood cells, which make up almost half the volume of blood. Other components of blood include white blood cells, which combat infections, and platelets, tiny cells that help to form blood clots to seal damaged blood vessels.
Disorders of the blood may be caused by an abnormality in the number, content, or form of one or more of the different types of blood cell. The first articles in this section deal with the different types of anaemia and with sickle-cell disease. In these disorders, haemoglobin, the oxygen-carrying pigment in red blood cells, is deficient or abnormal, or red cells are destroyed at an accelerated rate. Disorders in which the blood either fails to clot or clots too readily are then discussed. Some of these disorders are inherited, such as haemophilia, Christmas disease, and von Willebrand’s disease. In these disorders, the genes that are responsible for producing specific clotting factors are either absent or abnormal. Various cancers of the blood, called leukaemias, are also discussed. These disorders result from an overproduction of white blood cells, which suppresses the production of the normal blood cells in the body. The final article in this section deals with polycythaemia, a condition in which too many red blood cells are produced.
For more information on the structure and function of blood, see Formation of Blood Cells.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.