Page 39 - Libro 2

2 — Arterial Physiology
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Figure 2-3 A diagram illustrating the cross-sectional area of the vascular system.
where V is velocity, Q is volume flow, and A is area. Given a constant flow, velocity will vary inversely related to the cross-sectional area. Thus, if the flow is the same, the velocity must increase if the area of a blood vessel decreases (Fig. 2-2). This change in velocity allows one to estimate the degree of cross- sectional stenosis within an individual vessel such as the internal carotid artery.
Throughout the entire circulatory system, the cross-sectional area increases from the aorta moving through the arteries, then arterioles, and finally into the capillaries (Fig. 2-3). Blood velocity thus decreases as blood travels from the aorta, through the arteries, then the arterioles, and finally through the capillaries. This slowing down of blood flow at the capillary level is important in the proper exchange of nutrients and