Peripheral resistance
Resistance to blood flow depends mainly on the diameter of blood vessels and the viscosity of blood. Smaller vessel diameter and higher blood viscosity lead to increased resistance, which can affect blood pressure and flow rates.
Pressure and temperature are the two factors that affect flow and viscosity. Viscosity refers to the resistance of a liquid to the shear forces.
Blood carries white blood cells, red blood cells, hormones and other substances. Internal friction within in the blood (viscosity) is caused by the percentage of these cells in the blood. A higher percentage of cells in the blood means the viscosity is higher. Red blood cells are the hematocrit. When the hematocrit is decreased such as occurs with anemia, the viscosity of the blood is decreased.
Viscosity increases
Blood viscosity is measured by a test called a viscometer, which determines how easily blood flows. Factors that can affect blood viscosity include temperature, hematocrit levels, and the presence of certain proteins or diseases.
Blood cells are erythrocyte, leukocyte and platelets but the hematocrit is the percentage of the erythrocytes out of the total blood volume.Blood viscosity is a measure of the resistance of blood to flow, which is being deformed by either shear stress or extensional stress.So the relation of between them is they will all talk about blood flow and number of cells of the blood in a range of blood volume.**The relationship is that when red blood cells increases, hematocrit increases, and blood viscosity also increases because too much red blood cells (erythrocytes) in the blood makes the blood more dense/thicker, and therefore slows down the flow of the blood. In short, blood cells, hematocrit, and blood viscosity are all directly proportional with each other.
Vasodilation and decreasing blood viscosity
An important source of resistance to blood flow is not low blood viscosity, as low viscosity would actually decrease resistance. The important sources of resistance to blood flow are vessel diameter, vessel length, and blood viscosity.
When the viscosity of a substance is low, it flows more easily and quickly.
Resistance is determined by three properties: the lengthand cross-sectional area of a material, and its resistivity. Since resistivity is affected by temperature, you could say that temperature indirectly affects resistance.
Vasodilation and decreasing blood viscosity
Blood viscosity is the most important efect on blood velocity. Viscosity meaning how thin or thick the blood is. Velocity meaning the flow of blood. If the blood is too thick it's velocity will be slow. If the blood is thin, the blood will flow faster.