For a better understanding of this disease it is necessary to know the blood cells and their functions.
Illustration by Carmen Bueno
The blood consists of a liquid called plasma and three distinct cell groups, each of which performs its own specific action.
The White blood cells or leukocytes are the body's defence against infections and strange substances that enter the system. To defend the body successfully, it is necessary for a sufficient number of white blood cells to exist in order to make adequate response, to arrive where they are needed, and to destroy and control the damaging microorganisms and substances. Similar to all blood cells, the white blood cells are produced in the bone marrow. They are formed from the precursor cells (stem cells) which mature until they convert into one of the 5 principle white blood cell forms: the neutrophils, the lymphocytes, the monocytes, the eosinophils and the basophils. A person produces approximately 100 billion white blood cells each day.
The red blood cells or haematids, or erythrocytes carry out the function of transporting oxygen from the lungs to the tissue and returning to the lungs with carbon dioxide for exhaling. The erythrocytes give blood its characteristic red colour.
• The platelets or the thrombocytes, work to clot the blood when a blood vessel is ruptured.
All the blood cells are the result the differentiation and maturing of the hematopoietic stem cells. In an adult the stem cells are located in the bone marrow, the soft and spongy substance that can be found inside the bones.
Transformation of the blood cells
Under normal conditions, the production of the blood cells is controlled in order to meet the body's precise needs. The alteration of this balance can cause a range of diseases: some are caused by an insufficient production of all the blood cells (bone marrow aplasia) or with a focus on some of the blood cell types (erythroblastopenia, megakaryocytopenia, agranulocytosis; others are caused by the production of cells that are incapable of performing their functions and in insufficient quantities (myelodysplastic syndrome) and finally others are the result of the production of a large number of cancerous cells (leukaemia).
For more information, please consult the following sources:
- Video about the production of red blood cells which can be found in the Medical encyclopaedia, Medline.
- Video about the immune system which can be found in the Medical encyclopaedia, Medline.
(illustrations by Mercè Capdevila, sourced from the Bone Marrow transplant guide (SPANISH))