Red blood cells Flashcards
What’s the first cell recognisable as an RBC precursor?
Proerythroblasts
Name 4 properties of proerythroblasts
They’re relatively large cells
They have clearly visible nuclei
They have loose, lacy chromatin
They have basophilic cytoplasm
What hormone is responsible for stimulating the production of RBCs by erythropoiesis and where’s it produced?
Erythropoietin is produced in the kidneys
What’s the function of hypoxia-inducible transcription factor HIF?
HIF enhances the expression of iron-absorbing genes
What’s the function of hepcidin?
Hepcidin is a key regulator of the entry of iron into circulation in mammals.
What is iron important to in RBC production?
The synthesis of haemoglobin
Name 4 causes of iron deficiency
Blood loss
Low dietary iron intake
Reduced absorption, due to coeliac disease, a gastrectomy or gastric bypass
Increased demands due to pregnancy or a growth spurt
What is cyanocobalamin another name for?
Vitamin B12
What are the 2 important metabolic functions of vitamin B12?
1) B12 acts as a coenzyme for methionine synthase in the methylation of homocysteine to methionine in cytosol
2) B12 acts as a coenzyme in the conversion of L-methylmalonyl coenzyme A to succinyl coenzyme A in the mitochondria, which is essential for RBC maturation and DNA synthesis
What does B12 deficiency cause?
Abnormal and diminished DNA, which leads to failure of nuclear maturation.
Why does vitamin B12 deficiency result in megaloblastic anaemia?
The active forms of folate cannot be formed and DNA synthesis fails
What is folate?
Folate is a B-vitamin (B9) required to produce white and red blood cells in the bone marrow, as well converting carbohydrates into energy and producing DNA and RNA
What is megaloblastic anaemia?
A condition in which the bone marrow produces unusually large, structurally abnormal, immature red blood cells (megaloblasts).
Name 3 reasons for vitamin B12 deficiency
- Inadequate intake through diet
- Acquired disorders of B12 absorption
- Inherited disorders of B12 absorption
Name 3 haematological tests for B12 deficiency
- Full blood count
- Blood film
- Bone marrow examination
How is folate essential to DNA synthesis?
Folate acts as a coenzyme in the synthesis of thymidine triphosphate
Name 4 causes of folate deficiency
- Inadequate dietary intake
- Absorption defects such as coeliac disease, Crohn’s disease, tropical sprue and alcohol abuse
- Increased demand due to pregnancy, haemolysis or cancer
- Antifolate drugs such as anticonvulsants, methotrexate or metformin
What is tropical sprue?
An acquired malabsorptive condition of probable infectious aetiology. Features include altered small bowel mucosa, chronic diarrhoea and signs and symptoms of multiple vitamin and nutrient deficiencies
What is hereditary spherocytosis?
Loss of membrane integrity allows the RBCs to become spherical. This is a common hereditary haemolytic anaemia in Northern Europe.
What is thalassaemia?
Any group of hereditary haemolytic diseases caused by faulty haemoglobin synthesis
What are the 2 main red blood cell enzymes?
Glucose-6-phosphate dehydrogenase (G6PD) and pyruvate kinase (PK).
What metabolises 10% of red cell glucose?
The hexose monophosphate shunt (HMS), aka the pentose phosphate pathway (PPP)
What enzyme is involved in the pentose phosphate pathway?
G6PD
What’s an important product of the pentose phosphate pathway?
NADPH, which plays a role in protecting the RBC from oxidative damage
