 hemorheology, also spelled haemorheology (from the greek âÎ±á¼·Î¼Î± haima "blood" and rheology), or blood rheology, is the study of flow properties of blood and its elements (i.e. blood plasma and cells). proper tissue perfusion can occur only when blood's rheological properties are within certain levels. alterations of these properties play significant roles in disease processes. blood viscosity is determined by plasma viscosity, hematocrit (volume fraction of red blood cell, which constitute 99.9% of the cellular elements) and mechanical properties of red blood cells. red blood cells have unique mechanical behavior, which can be discussed under the terms erythrocyte deformability and erythrocyte aggregation. because of that, blood behaves as a non-newtonian fluid. as such, the viscosity of blood varies with shear rate. blood becomes less viscous at high shear rates like those experienced in peak-systole. contrarily, during end-diastole, blood moves more slowly and becomes thicker and stickier. therefore, blood is a shear-thinning fluid. == blood viscosity == blood viscosity is a measure of the resistance of blood to flow. it can also be described as the thickness and stickiness of blood. this biophysical property makes it a critical determinant of friction against the vessel walls, the rate of venous return, the work required for the heart to pump blood, and how much oxygen is transported to tissues and organs. these functions of the cardiovascular system are directly related to vascular resistance, preload, afterload, and perfusion, respectively. the primary determinants of blood viscosity are hematocrit, red blood cell deformability, red blood cell aggregation, and plasma viscosity. plasma's viscosity is determined by water-content and macromolecular components, so these factors that affect blood viscosity are the plasma protein concentration and types of proteins in the plasma.{{cite journal |author=kÃ©smÃ¡rky 
Blood Blood_tests Hematology