Figure 8.15: Valves ensure that blood flows one only way though veins.Comparison between arteries, veins and capillaries DUMMY
Arteries Capillaries Veins
blood movesawayfrom
the heartblood supply at tissue level bloodreturnedto the heartthick middle layer of
involuntary muscle to
increase or decrease
diameterone layer of endothelium
with very small diameterthin middle layer as
pressure is reducedinner layer of endothelium
which reduces frictiononly endothelium layer
presentlarger diameter of inner
cavity, lined with
endothelium to reduce
friction
situated deeper in the
tissue to maintain body
temperaturesituated at tissue level only situated near the surface of
the skin to release heatno valves except in the
base of the aorta and the
pulmonary arteriesno valves present semi-lunar valves are
present at intervals, to
prevent back flow of blood
blood always under high
pressureblood is under high
pressure where red blood
cells are forced to flow
through in single fileblood is under low
pressurea pulse can be felt as blood
flowsno pulse no pulse can be detectedTable 8.1: Table comparing arteries, capillaries, and veinsSee video: SHORTCODEat http://www.everythingscience.co.za238 8.2. Circulatory systems in animals