<prompt> Flow is laminar in small vessels becauseReynolds number is 2000Total cross sectional area of small vessels is smallerDiameter of smaller vessels is lessEffective velocity in small vessels is less  <response>: The most important determinant of flow of blood in small blood vessels is effective velocity. The velocity is inversely proportional to the cross-sectional area. In the case of small vessels, the cross-sectional area is large. So the effective velocity is low. When the velocity is low, flow is laminar. 