Aorta pressure/cross-sectional area

The geometrical parameters of the canine systemic and pulmonary circulations are summarized in Table 56.1. Vessel diameters vary from a maximum of 19 mm in the proximal aorta to 0.008 mm (8 m) in the capillaries. Because of the multiple branching, the total cross-sectional area increases from 2.8 cm in the proximal aorta to 1357 cm in the capillaries. Of the total blood volume, approximately 83% is in the systemic circulation, 12% is in the pulmonary circulation, and the remaining 5% is in the heart. Most of the systemic blood is in the venous circulation, where changes in compliance are used to control mean circulatory blood pressure. This chapter will be concerned with flow in the larger arteries, classes 1 to 5 in the systemic circulation and 1 to 3 in the pulmonary circulation in Table 56.1. Flow in the microcirculation is discussed in Chapter 59, and venous hemodynamics is covered in Chapter 60. 

By measuring the static elastic properties of human thoracic and abdominal aortas in vitro, Langewouters et al. [35] proposed the following empirical relationship between the cross-sectional area of the lumen (A) and the pressure in the vessel (p) ... 

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