Capillaries, the smallest blood vessels of the body, connect the arterial system with the venous system and supply our tissues with oxygen and nutrients (Figure 1.8). It is estimated that if all of the capillaries of an average adult were unwound and spread out end to end, they would extend to a length of about 64 000 km.

(a) How many miles is this length?

(b) Compare this length with the circumference of the Earth.

THINKING IT THROUGH. 

(a) This conversion is straightforward – just use the appropriate conversion factor.

(b) How is the circumference of a circle or sphere calculated? There is an equation to do so, but the radius or diameter of the Earth must be known. (If you do not remember one of these values, see the solar system data table inside the back cover of this book.)

Transcribed Image Text:

Arterioles Artery Capillaries Venules Vein FIGURE 1.8 Capillary system Capillaries connect the arterial and venous systems in our bodies. They are the smallest blood vessels, but their total length is impressive. See Example 1.4.