he hematocrit of the blood leaving the heart is about 40%. When it enters the microcirculation however, the average red blood cell concentration may change. Explain why this happens in: • A 50 micron diameter arteriole • The reticular network of the spleen • Capillary network • List at least 3 factors which could affect the viscosity of blood in large vessels (> 1mm) • Explain why the viscosity of blood changes as it enters smaller vessels (down to 10 microns) • List two factors which could impede the movement of blood through capillaries (<10 microns)
Added by Dolores B.
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In larger vessels, such as those leaving the heart, the hematocrit is around 40%. However, as blood flows through smaller vessels, the concentration of RBCs can change due to various factors. Show more…
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For blood with a hematocrit rate of 45%, consider that the yield shear stress is approximately y = 0.05 dynes/cm^2. Use the Casson's Model for the rheology of blood (seen in the presentation of Fundamental Concepts) and the graph indicated in the figure below to determine if, for each of the vessels in the table shown, the blood flow can be considered a Newtonian fluid or Non-Newtonian. You must technically support your answer. Graph of effective viscosity versus cutting speed for blood of different hematocrits (H): Note the Newtonian behavior of the fluid at zero hematocrit and the logarithmic vertical scale. •: Pure blood; x: Defibrinated blood (i.e. blood from which fibrinogen coagulation protein has been removed); o: Cells in Ringer's solution. Modified with permission from the American Physiological Society of Chien et al. Vessel | Mean velocity (cm/s) | Radius (cm) Ascending aorta | 20 | 0.75 Abdominal artery | 15 | 0.45 Femoral artery | 10 | 0.2 Arteriole | 0.3 | 0.0025 Inferior vena cava | 12 | 0.5
Sri K.
The human circulatory system consists of a complex branching pipe network ranging in diameter from the aorta (largest) to the capillaries (smallest). The average radii and the number of these vessels are shown in the table. Does the arerage blood velocity increase, decrease, or remain consiant as it travels from the aorta to the capillaries?
The human circulatory system consists of a complex branching pipe network ranging in diameter from the aorta (largest) to the capillaries (smallest). The average radii and the number of these vessels are shown in the table, Does the average blood velocity increase, decrease, or remain constant as it travels from the aorta to the capillaries? $$\begin{array}{lcc} \hline \text { Vessel } & \text { Average Radius, mm } & \text { Number } \\ \hline \text { Aorta } & 12.5 & 1 \\ \text { Arteries } & 2.0 & 159 \\ \text { Arterioles } & 0.03 & 1.4 \times 10^{2} \\ \text { Capillaries } & 0.006 & 3.9 \times 10^{9} \\ \hline \end{array}$$
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