Erythrocytes can not sedimentate inside blood vessels. Due to:
constant blood movement;
the charge of blood vessel wall and the charge of erythrocyte is the same (negative) so cells repel from it.
If we put the blood inside the test-tube and add anticoagulant than in few minutes we can observe the sedimentation of erythrocytes, because the density of erythrocytes (1,090 g/cm3) is higher, than the density of blood plasma (1,025 – 1,034 g/cm3). The mechanism of the process is as follows. At first erythrocytes form complexes with each other (10-12 erythrocytes form “monetary column”). After these complexes interact with plasma proteins, they become heavier and they start to settle faster. Due to this process is not equable in time (slow in the beginning, faster in the end) ESR is determined for the fixed period of time, usually 1 hour.
In normal state ESR of men is 2-10 mm/hour, of women 2-15 mm/hour.
Factors, which affect ESR
The main mechanism of influence of all factors is the changes in stickiness. There is inversed dependence between stickiness and ESR (the higher stickness – the lower ESR, the lower stickness – the higher ESR). That means that the factors, which increase stickiness – they decrease ESR and otherwise.