Small vein

Larger venules transition into small veins where all three tunics are well represented. Also appearing in small veins are valves which are formed by paired, crescent-shaped folds (leaflets) of the tunica intima that project into the lumen. These valves help prevent the back flow of blood. Small veins have a tunica media composed of circularly-arranged smooth muscle cells. 200x

Valves are particularly prominent in veins of the lower extremity where they prevent the “back-flow” of blood due to gravity. Blood pressure on the venous side of the circulatory system is low and venous return to the heart is accomplished principally by contraction of adjacent skeletal muscles, which produce a milking action in the vein.

Larger venules transition into small veins where all three tunics are well represented. Also appearing in small veins are valves which are formed by paired, crescent-shaped folds (leaflets) of the tunica intima that project into the lumen. These valves help prevent the back flow of blood. Small veins have a tunica media composed of circularly-arranged smooth muscle cells. 200x

Larger venules transition into small veins where all three tunics are well represented. Also appearing in small veins are valves which are formed by paired, crescent-shaped folds (leaflets) of the tunica intima that project into the lumen. These valves help prevent the back flow of blood. Small veins have a tunica media composed of circularly-arranged smooth muscle cells. 200x

This image was taken of a slide from the University of Mississippi slide collection.