Arterioles have less elastic tissue but have smooth muscle. When arterioles constrict, blood pressure increases. At the arteriole end of a capillary, fluids and nutrients are forced out into tissues. At the venule end, fluids with wastes reenter the bloodstream.
Lymphatic capillaries drain excess tissue fluid.
Shunting of blood is possible via thoroughfare channels that bypass capillary beds. These vessels have the same layers as arteries but have less muscle. It has a septum, atrioventicular valves, chordae tendineae, and semilunar valves. Each heartbeat is called a cardiac cycle. Heart sounds can be heard as the respective valves close.