Blood, Marrow & the EPO Loop

One factory, many products · Week 9
The kidneys watch the oxygen level. When oxygen runs low they release erythropoietin (EPO), and the marrow builds more red cells. Pick a situation, then drag the weeks slider and watch the labs move.

The loop in one picture

The spun tube on the left shows plasma over packed red cells. The kidney sends EPO to the marrow. The arrow gets fatter as EPO rises.
Plasma, about 55% Buffy coat Packed red cells = hematocrit
Pick a situation.

What the marrow is shipping

Each row fills up as that cell line is made. Watch all three rows at once.
Healthy bloodHgb 15, Hct 45%, EPO steady

Pick a situation

Weeks since the change0
Hemoglobin
15.0
g/dL · 12–16 normal
Hematocrit
45
% · about 3 × Hgb
EPO
10
mU/mL · 5–25 normal
Retic count
1.0
% · new red cells
White cells
7.0
K/µL · 5–10 normal
Platelets
250
K/µL · 150–400
What is happening now
Pick a situation to begin.
One factory, many products. When the red cells, the white cells, and the platelets all fall together, that is pancytopenia. It points at the marrow itself, not at three separate problems.