Misconception 16. The total surface area of all capillaries in an adult human is approximately 6.3 square meters.
It takes roughly 20 months for 1 ml of blood to pass through a single capillary. This is based on the velocity of flow (approx. 1 mm/sec.), the number of erythrocytes per ml of blood (approx. 5 x 109), and the fact that erythrocytes usually traverse capillaries single file.
It is only for the fact that there are so many capillaries (>109) that the cardiac output (5000 ml/min) can be readily moved through the total body capillaries. Due to the very large number of capillaries, the average diameter (5 um), and the average length (1-2 mm), the total internal surface area of all of the capillaries is approximately 6,300 sq. meters. This large area is nearly the size of a baseball field, and is consistent with the exchange function of these vessels.
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