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Unformatted text preview: • since small arteries and arterioles are narrow they provide the greatest resistance to blood flow . • arterioles are the main site of variable resistance in the systemic circulation. . CAPILLARIES. • the arterial system branches very extensively. • the branching is so great that each cell in the body is no more than 80 micrometers away from a capillary. • the walls of capillaries are only 1 cell thick. • so there is a rapid exchange of material between the blood and the tissues. . VEINS. • the average pressure in veins is low compared to that in the arterial system • veins contain valves (these are not found in arteries). 4/6/08 1:06 AM Biology141 (Physiology) Page 2 of 2 https://courses.bio.psu.edu/spring2008/biol141/Background%20to%20blood%20vessels2.htm...
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This note was uploaded on 04/05/2008 for the course BIOL 141 taught by Professor Viti,janehartwel during the Spring '08 term at Pennsylvania State University, University Park.
- Spring '08