Rheology is the study of the deformation and flow of matter. The term rheology was coined by Eugene Bingham, a professor at Lehigh University, in 1920, from a suggestion by a colleague, Markus Reiner. The term was inspired by Heraclitus's famous expression panta rei, "everything flows".
Hemodynamics (literally "blood dynamics") is the study of the properties and flow of blood. Blood is pumped via the heart throughout the cardiovascular system. Oxygenated blood leaves the heart via a series of large arteries. As the blood travels further along these arteries the diameter becomes smaller and they the vessels become arterioles. These arterioles become capillaries and eventually venules, where deoxygenated blood passes through networks of veins back to the heart. The arteriole-capillary-venule junctions compose most of the area of the vascular system and allow the transfer of the most vitamins and nutrients.
Rheology is the science of deformation and flow. One common factor between solids, liquids, and all materials whose behavior is intermediate between solids and liquid is that if we apply a stress or load on any of them they will deform or strain. For our purposes we will use the term to describe the dynamics between blood clotting (moving towards a solid state) or blood thinning (moving towards a liquid state). It might be tempting to substitute the word 'viscosity' for rheology when talking about blood types and clotting, but it does not cover the 'dynamics' of how, when and why blood can change texture; it only distinguishes one texture state form another. As we will see, your blood type has a very potent effect on the rheology of your blood.
There are profound differences between the blood types with regard to rheology of their clotting chemistries. These differences are very significant reasons why the blood types tend to polarize with regard to their tendencies, with more blood types A and AB having much more easily clotting blood, and type O and B having blood which does not clot as readily.
Differences between the blood types in blood thickness have been also reported in depression (1) high blood pressure, 2) stress, (3) diabetes, (4) heart attack and thyroid disease, (5) kidney failure (6) and malignant melanoma. (7)
1. Dintenfass L, et al. Blood rheology in patients with depressive and schizoid anxiety. Biorheology. 1976 Feb;13(1):33-6.
2. Dintenfass L, et al. Dynamic blood coagulation and viscosity and degradation of artificial thrombi in patients with hypertension. Cardiovasc Res. 1970 Jan;4(1):50-60
3. Dintenfass L, et al. Effect of stress and anxiety on thrombus formation and blood viscosity factors. Bibl Haematol. 1975;(41):133-9.
4. Dintenfass L, et al. Genetic and ethnic influences on blood viscosity and capillaries in diabetes mellitus. Microvasc Res. 1977 Sep;14(2):161-72.
5. Dintenfass L, et al Effect of fibrinogen on aggregation of red cells and on apparent viscosity of artificial thrombi in haemophilia, myocardial infarction, thyroid disease, cancer and control systems: effect of ABO blood groups. Microvasc Res. 1975 Jan;9(1):107-18.
6. Dintenfass L, et al . Formation, consistency and degradation of artificial thrombi in severe renal failure. Effect of ABO blood groups. Thromb Diath Haemorrh. 1968 Nov 15;20(1):267-84.
7. Dintenfass L. Some aspects of haemorrheology of metastasis in malignant melanoma. Haematologia (Budap). 1977;11(3-4):301-7.