Page 6, Architecture of the Circulation, Dr. D. Penney
Circulation Symmetry (continued..)
Total surface area also increases enormously at the capillary level (6,300 m2), a fact consistent with their exchange function. While the aorta is as much as 1/2 meter in length, capillaries are only about 1 mm in length; however, because capillary flow velocity is so much slower through capillaries, the transit time through each of these vessels is approximately the same, 1-2 seconds. Regardless of the huge number of capillaries, their total blood volume is remarkably small. This is also true of the arteries and arterioles. Most of the blood volume is held in the main venous branches and the large veins, previously referred to as the capacitance vessels. See misconception number 11.
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