Red Blood Cells Flashcards
What is haemopoesis?
The formation and development of blood cells
What are HSC’s?
Haemopoieitic Stem Cells, which give rise to lymphoid stem cells and myeloid stem cells- from which red blood cells arise.
Two essential characteristics of HSC’s?
They can self-renew and differentiate to mature progeny
Sites of haemopoesis in the fetus?
Yolk sac (mesoderm), then liver and then bone marrow
4 factors required for erythropoiesis?
Iron, Vitamin B12, Folate and erythropoietin (regulator)
Microcytic vs macrocytic anaemia?
Iron deficiency vs B12/folate deficiency
Where is erythropoietin synthesised?
The kidney
Two major functions of iron?
- Oxygen transport in haemoglobin
- Mitochondrial proteins cytochromes a,b and c, ATP production (vital co-factor for many enzymes and proteins involved in metabolism)
What synthesis are Vitamin B12 and folate used for?
dTTpP which is used in thymidine. Therefore, lack of Vitamin B12 and folate inhibits DNA synthesis and cell divison.
What factor does B12 combine with?
Intrinsic Factor (IF) made in the gastric parietal cells
Autoimmune disorder due to inadequate secretion of IF?
Pernicious anaemia
Where is folic acid absorbed?
small intestine
Erythrocyte life span?
120 days
3 factors that affect erythrocyte function?
- Integrity of the membrane
- Haemoglobin structure and function
- Cellular metabolism
What shape are erythrocytes and how does this help them?
Biconcave which helps their maneuverability through small blood vessels
What is hereditary spherocytosis?
When RBC’s are spherical in shape due to a genetic defect that causes disruption of vertical linkages in the membrane. They are less flexible and are removed prematurely by the spleen (haemolysis)
What does the disruption of horizontal linkages in the membrane produce?
Hereditary Elliptocytosis
What two things are RBC metabolism highly adapted for?
- Generation of ATP to meet energy requirements
- Maintenance of haemoglobin, membrane integrity and RBC volume
RBC sizes?
- Microcytic- smaller RBC’s due to iron deficiency, anaemia or defects in globin synthesis (alpha or beta thalassaemia)
- Normocytic- normal RBC’s
- Macrocytic- larger RBC’s (round, oval or polychromatic-blue tinged) due to Vitamin B12 and folic acid deficiency, liver disease, haemolysis or pregnancy. Cells grow in size as they cannot undergo cell division or DNA synthesis.
RBC colour
- Normal RBC’s have a third of the diameter that is pale due to the centre having less haemoglobin
- Hypochromia- when RBC’s have a larger lighter area due to having a flatter shape and lower haemoglobin content. Goes with microcytosis
- Polychromasia- describes a blue tinge to the RBC’s, indicating that the cell is young. Causes macrocytosis
What is poikilocytosis?
When RBC’s show more variation in shape than normal
