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14. The structure, function and origin of erythrocytes: Difference between revisions

14. The structure, function and origin of erythrocytes (view source)

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(Created page with "== Red blood cells == thumb|Structure of red blood cells RBCs are small cells in the blood. They’re red, which is why the blood is red as well. RBCs are 7 – 8 µm in diameter, and they have a ''biconcave disc'' shape, which is difficult to explain but easier to show. The shape is important because it allows the cells to be flexible. The RBCs must squeeze through very small vessels called capillaries, which may be around 5 – 10 µm in dia...")
 
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Measuring the mean RBC size can be important in determining whether there is microcytosis or macrocytosis. This is done by taking a blood sample, measuring the diameter of the RBCs and plotting it into a curve. This curve is called a Price-Jones curve, and in healthy people will almost all RBCs be around 7-8 µm, so there will be a peak there.
Measuring the mean RBC size can be important in determining whether there is microcytosis or macrocytosis. This is done by taking a blood sample, measuring the diameter of the RBCs and plotting it into a curve. This curve is called a Price-Jones curve, and in healthy people will almost all RBCs be around 7-8 µm, so there will be a peak there.
 
[[File:Price-Jones curve.png|thumb|A Price-Jones curve. The x-axis shows the diameter of the RBCs in micrometres. The y-axis shows the number of RBCs. This figure shows the situation for healthy people (red) and for pernicious anaemia (B12 deficiency anaemia) in blue.]]
If the peak is lower, i.e. below 7 µm there is microcytosis, which indicates iron deficiency anaemia. If the peak is higher, i.e. above 8 µm there is macrocytosis, which indicates B12 or folate deficiency anaemia. The curve looks like this:
If the peak is lower, i.e. below 7 µm there is microcytosis, which indicates iron deficiency anaemia. If the peak is higher, i.e. above 8 µm there is macrocytosis, which indicates B12 or folate deficiency anaemia.  
 
A Price-Jones curve. The x-axis shows the diameter of the RBCs in micrometres. The y-axis shows the number of RBCs. This figure shows the situation for healthy people (red) and for pernicious anaemia (B12 deficiency anaemia) in blue.


The average volume of each red blood cell is called mean corpuscular volume (MCV). Its normal value is 80-95 fL. The f stands for femto-, which is one billionth of a µL. This value is elevated in macrocytosis and decreased in microcytosis. MCV can be calculated like this: MCV = haematocrit / RBC count.
The average volume of each red blood cell is called mean corpuscular volume (MCV). Its normal value is 80-95 fL. The f stands for femto-, which is one billionth of a µL. This value is elevated in macrocytosis and decreased in microcytosis. MCV can be calculated like this: MCV = haematocrit / RBC count.