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This is because the pressure in the cuff is high enough such that it completely occludes the blood flow. This is similar to a flexible tube or pipe with fluid in it that is being pinched shut. If the pressure is dropped to a level equal to that of the patient's systolic blood pressure, the first Korotkoff sound will be heard.
In the arterioles blood pressure is lower than in the major arteries. This is due to bifurcations, which cause a drop in pressure. The more bifurcations, the higher the total cross-sectional area, therefore the pressure across the surface drops. This is why [citation needed] the arterioles have the highest pressure-drop. The pressure drop of ...
Consequently, if a liquid has dynamic viscosity of n centiPoise, and its density is not too different from that of water, then its kinematic viscosity is around n centiStokes. For gas, the dynamic viscosity is usually in the range of 10 to 20 microPascal-seconds, or 0.01 to 0.02 centiPoise. The density is usually on the order of 0.5 to 5 kg/m^3.
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.
The Fåhræus–Lindqvist effect (/ f ɑː ˈ r eɪ. ə s ˈ l ɪ n d k v ɪ s t /) or sigma effect [1] describes how the viscosity of blood changes with the diameter of the vessel it travels through. In particular there is a decrease in viscosity as the vessel diameter decreases, but only at small diameters of 10–300 micrometers (mainly ...
As the blood moves into the aortic arch, the area with the highest velocity tends to be on the inner wall. Helical flow within the ascending aorta and aortic arch help to reduce flow stagnation and increase oxygen transport. [4] As the blood moves into the descending aorta, rotations in the flow are less present.
Blood pressure varies over longer time periods (months to years) and this variability predicts adverse outcomes. [18] Blood pressure also changes in response to temperature, noise, emotional stress, consumption of food or liquid, dietary factors, physical activity, changes in posture (such as standing-up), drugs, and disease. [19]
If a fluid has a high viscosity, it will not flow as easily as a fluid with a lower viscosity. Because this relates directly to the strength of the attraction between the fluid molecules, viscosity of blood decreases with increasing temperature and decreasing hematocrit. It also lowers with a higher shear, which is why it is classified as a ...