Red Blood Cells Flashcards
How much blood should a 70kg adult have?
5L of blood.
What proportions should an adult’s blood be?
40% cells and 60% plasma.
How many times more numerous are RBC than WBC?
x500.
How often fo RBC need to replace?
RBC need to replace 1% per day to make up for the expected lifespan of 100 days.
What is the structure of a RBC?
Biconcave disc with no nucleus.
How does the structure of a RBC give it qualities?
Pliable with high surface area to volume ratio.
What does the RBC contain within it?
Bag of haemoglobin and enzymes for glycolysis- unable to make no proteins or divide.
How does the RBC prevent oxidation?
By maintaining membrane integrity.
What forms “blood islands”?
Embryological stem cells form blood islands in the yolk sac.
What is the cell pathway in the foetus?
Cells migrate to the liver then spleen and then bone marrow.
How does the distribution of bone marrow change as we grow?
At birth bone marrow is widely distributed, retreating to axial skeleton by adulthood.
What are the growth factors associated with RBCs?
Interleukin 3, erythropoietin, androgens and thyroxine.
What is in the stroma of bone marrow?
Fibroblasts, macrophages, endothelium and fat cells.
What is a reticulocyte?
An immature RBC.
What is reticulin?
Remnants of mRNA left once the nucleus of a maturing RBC has been extruded.
How is the reticulin removed?
In the spleen in 1-2 days.
What can reticulocyte numbers be used to measure?
A useful measure of marrow response to anaemia or treatment.
What can be used to stain reticulocytes?
New methylene blue on slide.
How much iron do adults have and where is most of it?
3000-5000mg of iron, 2/3 being in the haemoglobin.
Where is ferrous iron transported to?
Transported into duodenal enterocytes.
What regulates iron absorption and release?
Hepcidin regulates iron absorption and release from macrophages.
When is the action of hepcidin increased?
In inflammatory disease hence less iron available.
Is there a mechanism to excrete iron?
No
How can humans lose iron?
Menstrual loss, minor trauma, GI, blood sampling and very small amounts in urine and skin shedding.
What is transferrin?
Glycoprotein found in blood plasma.
What is the function of transferrin?
Is capable of binding iron and thus acts as a carrier of iron in the bloodstream.
What is the function of ferritin?
An iron protein complex that is one of the forms in which iron is stored in tissues (insoluble).
What is the daily requirement of folic acid/folate?
0.1mg.
Where is folate absorbed?
Upper small bowel.
Where is folate stored and how much is stored?
In the liver and 10-20mg.
What is folate and its function?
B vitamin that is important in the synthesis of nucleic acids.
What is the daily requirement of B12 (cobalamin)?
1 microgram all derived from animal products.
What produces the “intrinsic factor” and what does it do?
Gastric parietal cells and it binds to B12.
Where is B12 absorbed?
In the terminal ileum.
What is B12 transported on?
Transcobalamin II via portal circulation to the liver.
Why do RBCs need B12?
Required to change from 5 methyl tetrehydrofolate to THF.
What is erythropoietin?
A hormone secreted by certain cells in the kidney in response to a reduction in the amount of oxygen reaching the tissues.
What controls erythropoiesis?
Erythropoietin increases the rate of RBC production and is the mechanism which controls erythropoiesis.
What is erythropoiesis?
RBC production.
What is the structure of erythropoietin?
GLycosylated 165 AA protein
Where is erythropoietin produced?
90% renal and 10% liver.
What are the medical uses of erythropoietin?
Useful recombinant drug for renal anaemia and myelodysplasia.
What switches on production of erythropoietin?
Tissue hypoxia or anaemia, high altitude and epo producing tumours.
What is hypoxia?
Deficiency of oxygen in the tissues.
In terms of hormones, what happens at low oxygen levels in the tissues?
mRNA for epo is increased and epo is produced.
What is spherocytosis?
The presence in the blood of abnormally shaped RBCs.
What does haemoglobin need to form?
2 alpha chains and 2 beta chains.
How are the haemoglobin different in the fetus?
The 2 alpha chains are replaced by gamma chains.
What chromosome codes for the alpha chains?
16.
What chromosome codes for the beta chains?
11.
What is thalassaemia?
An inherited defect in globin chain production.
What causes sickle cell s disease?
One AA change in the beta chain.
Why do RBCs need enzymes?
For a glycolytic pathway ending with lactate and pyruvate producing energy.
What is energy needed for in RBCs?
Maintain membrane integrity, prevent oxidation of enzymes and to maintain ion gradients.
Which ions have gradients in the RBC?
Iron, calcium and potassium.
What would cause an oxygen dissociation curve to shift to the right?
Acidosis and increased temperature will cause a right shift and hence deliver more oxygen to tissues.
What does 2,3 diphosphoglycerate do?
An intermediate step in glycolysis produces a right shift of oxygen dissociation curve and hence more released in the tissues.
When is 2,3 DPG increased?
Exercise, anaemia and high altitude.
What is myoglobin?
An iron containing protein found in muscle cells. One haem unit, one globin chain.
What is the function of myoglobin?
Acts as a store for oxygen for immediate use.
What is the normal blood pH?
7.35-7.45.
Why is acidosis important for enzymes?
They work optimally at physiological pH.
What happens to cell membranes in acidosis?
They become leaky.
What happens to neurones in acidosis?
Become less able to transmit in acidosis.
What happens to neurones in alkalosis?
They become hyperactive.
What is the bicarbonate buffer equation?
carbon dioxide and water form carbonic acid which breaks down into hydrogen ions and bicarbonate.
What happens to the buffer equation when there is a decrease in pH?
A decrease in pH will drive the equation to the left.
What are the buffer equations catalysed by?
Carbonic anhydrase.
What is the buffer capacity of haemoglobin?
30%.
In terms of H+ what happens to haemoglobin after it loses its oxygen?
It combines with H+ and the low pH decreases haemoglobin affinity for oxygen.
What happens to the RBC as it ages?
Membrane becomes more rigid, loss of glycolytic enzymes and neoantigens exposed on CSM.
What happens to old RBCs?
Some lost from GI tract, some into tissues and some through menstrual loss while some are destroyed in the body.
What “mops up” free haemoglobin?
Haptoglobin- cleared by the liver, any excess can appear in the liver.
What happens to the globin once the RBC is destroyed?
Globin chains broken into AAs.
What happens to the iron once the RBC is destroyed?
Iron bound to transferrin and returned to macrophages.
What happens to the porphyrin ring once the RBC is destroyed?
Becomes bilirubin- bound to albumin and conjugated to glucuronide and then excreted in the bile.
What can low albumin levels indicate?
A problem with your liver or kidneys.
