When precapillary sphincters are relaxed, blood flows from the arteriole into the metarteriole, then passes freely through the capillary beds (the network of capillaries) where exchange of nutrients, gases, and wastes occurs. After passing through the capillaries, the blood flows into the postcapillary venules. If the precapillary sphincters were contracted, blood would bypass the capillary beds and flow directly through the thoroughfare channel from the metarteriole to the venule. Thus, the structures blood passes through when precapillary sphincters are relaxed are:

• Arteriole
• Metarteriole
• Capillary beds (capillaries)
• Postcapillary venules

This relaxation allows full perfusion of the tissue, enabling effective exchange between blood and the surrounding cells.