Why myeloid-erythroid ration is 4:1 while more RBC's in blood?

[tarekatpf]

In the bone marrow, the normal ratio of myeloid and erythroid series cells is 4:1. So, for every erythroid cell, there are four myeloid cells, which gives
But in the circulation, there are almost 1000 times more RBC's than total WBC's ( which also includes non-myeloid WBC's, such as lymphocytes. )

Why is it so?

 

[SW VandeCarr]

In the bone marrow, the normal ratio of myeloid and erythroid series cells is 4:1. So, for every erythroid cell, there are four myeloid cells, which gives
But in the circulation, there are almost 1000 times more RBC's than total WBC's ( which also includes non-myeloid WBC's, such as lymphocytes. )

Why is it so?

http://en.wikipedia.org/wiki/Bone_marrow

I'm not sure it is so. Myelopoietic cells constitute 56.6% of parenchymal cells while erythropoietic cells constitute 25.6% of such cells. Erythrocytes circulate for about 120 days while leukocytes circulate for about 3-4 days. This may explain part of the perceived imbalance. No teleologic explanation is required for the rest of the perceived imbalance, but it might be that the bone marrow holds a reserve of myelopoietic cells for emergencies.

EDIT: Allowing for the possibility of an error in my addition, it's still clear the ratio is closer to 2:1.