Health encyclopaedia - Alphabetical Topic List

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Anaemia is the general name for a range of disorders affecting red blood cells. Red blood cells contain haemoglobin, which is responsible for carrying oxygen in the blood. To produce red blood cells, the body needs iron, vitamin B12 and folic acid. If one or more of these is deficient, anaemia will develop. Red blood cells are produced in the bone marrow and circulate in the bloodstream before they are broken down in the spleen. If the level of red cells (and therefore of haemoglobin), in the blood is abnormally low the oxygen-carrying capacity of blood is reduced and anaemia develops.

Haemoglobin is measured in terms of the weight present in grams (g) per 100 millilitres (1 decilitre or dl) of blood. A normal level in females will lie somewhere between 11.5 and 15.5 g per dl, and in males between 13 and 18 g per dl. The normal range of red cell numbers per cubic millimetre of blood is 4,100,000–5,200,000 in females and 4,400,000–5,800,000 in males.

Iron deficiency anaemia is the most common type of anaemia. It affects up to 30% of the world’s population. Up to 14% of menstruating women in developed countries have iron deficiency anaemia. Megaloblastic anaemia (the red cells are megablastic i.e. large and abnormal) develops if vitamin B12 or folic acid are lacking. A lack of folic acid, leads to megaloblastic anaemia. Another type of megablastic anaemia is called ‘pernicious’ anaemia, in which there is insufficient absorption of vitamin B12 from the diet.

Haemolytic anaemia occurs as the result of an inherited or an acquired condition in which the body destroys red blood cells prematurely. Haemolysis describes the breaking up of red blood cells, resulting in the release of haemoglobin into the plasma. Aplastic anaemia results from the failure of the bone marrow to produce sufficient numbers of red blood cells.