Haematopoesis

What is haematopoesis?

The process by which blood cells are replaced.

How is haematopoesis regulated?

Haematopoetic growth factors promote differentiation and maturation of bone marrow stem cells into blood cells.

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.

What are the causes of anaemia?

1. Reduced red blood cell production2. 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-haemolysis5. Loss of circulating red blood cells- bleeding

Where and in what form is iron found in the body?

65% circulating as haemoglobin17.5% Liver Spleen and Bone Marrow as ferritin and haemosiderin17.5% Myoglobin, cytochromes and enzymes, unavailable for haemoglobin synthesis

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.

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.

Apart form erythropoeisis, what happens to ingested iron?

Forms myoglobin and enzymesStored as ferritinForms part of phagocytic cells

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.

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.

What are the functions of vitamin B12?

GrowthCell replicationHaematopoesisMyelin synthesis

What is required for B12 absorption?

Intrinsic factor secreted from the stomach.Inadequate secretion causes B12 deficiency and eventually pernicious anaemia.

What is the function of folic acid in its active form?

Amino acid biosynthesisSynthesis of purines and pyrimidinesCell proliferationErythropoeisis

What are the effects of folic acid deficiency?

Pregnant mother- spina bifida in the fetusNormal person- megaloblastic anaemia

What are haematopoetic growth factors? Name 2.

Endogenous glycoproteins that stimulate the differentiation and maturation of bone marrow progenitor cellseg Colony-stimulating factorErythropoeitin

Give a summary of Erythropoeitin.

Produced in the kidneys as a response to hypoxiaHemoprotein 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.