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What is haematopoesis?
The process by which blood cells are replaced.
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How is haematopoesis regulated?
Haematopoetic growth factors promote differentiation and maturation of bone marrow stem cells into blood cells.
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What is anaemia?
- A subnormal concentration of erythrocytes or haemoglobin in the blood.
- There are several types of anaemia.
- Nutritional anaemia is very common and is caused by deficiencies in Iron, vitamin B12 and Folic acid.
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What are the causes of anaemia?
- 1. Reduced red blood cell production
- 2. Defective precursor proliferation (caused by iron deficiency and marrow disorders)
- 3. Defective precursor maturation (caused by folic acid and vitamin B12 deficiency and toxins)
- 4. Increased rate of red blood cell destruction-haemolysis
- 5. Loss of circulating red blood cells- bleeding
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Where and in what form is iron found in the body?
- 65% circulating as haemoglobin
- 17.5% Liver Spleen and Bone Marrow as ferritin and haemosiderin
- 17.5% Myoglobin, cytochromes and enzymes, unavailable for haemoglobin synthesis
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What is the role of iron in the body? What characteristics makes it suitable for its function?
- Iron is an important component in haemoglobin and several enzymes.
- It can exist in several oxidation states.
- It can form stable co-ordination complexes.
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What happens to ingested iron?
- 10% of the iron is absorbed.
- It circulates in the plasma as transferrin.
- It moves to the bone marrow where it is packaged into new erythrocytes over 120 days.
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Apart form erythropoeisis, what happens to ingested iron?
- Forms myoglobin and enzymes
- Stored as ferritin
- Forms part of phagocytic cells
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What is the most commo form of Iron used to treat iron defficiency anaemia and what percentage of elemental iron is contained?
- Ferrous sulphate.
- Contains 20% elemental iron.
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Why are folic acid and vitamin B12 necessary?
- They are involved as cofactors in biosynthetic pathways.
- Defeciency in either of them causes megaloblastic anaemia, where DNA synthesis in the production of red blood cells is inhibited.
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What are the functions of vitamin B12?
- Growth
- Cell replication
- Haematopoesis
- Myelin synthesis
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What is required for B12 absorption?
- Intrinsic factor secreted from the stomach.
- Inadequate secretion causes B12 deficiency and eventually pernicious anaemia.
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What is the function of folic acid in its active form?
- Amino acid biosynthesis
- Synthesis of purines and pyrimidines
- Cell proliferation
- Erythropoeisis
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What are the effects of folic acid deficiency?
- Pregnant mother- spina bifida in the fetus
- Normal person- megaloblastic anaemia
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What are haematopoetic growth factors? Name 2.
- Endogenous glycoproteins that stimulate the differentiation and maturation of bone marrow progenitor cells
- eg
- Colony-stimulating factor
- Erythropoeitin
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Give a summary of Erythropoeitin.
- Produced in the kidneys as a response to hypoxia
- Hemoprotein receptors regulate the synthesis and release.
- Recombinant human erythropoeitin is used to treat anaemia caused by renal failure, chemotherapy and HIV treatments.
- Improve quality of life, reduce need for blood transfusions, increases haemoglobin levels.
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