Medium vein

Several criteria distinguish a medium vein from its accompanying medium (muscular) artery. Veins possess wider lumens, thinner walls and more irregular outlines than do arteries; longitudinally-oriented smooth muscle may be present in the tunica adventitia of veins. Additionally, veins possess valves, consisting of intimal folds, which are not present in arteries. Arteries can also be distinguished by their dominant tunica media. 100x

Several criteria distinguish a medium vein from its accompanying medium (muscular) artery. Veins possess wider lumens, thinner walls and more irregular outlines than do arteries; longitudinally-oriented smooth muscle may be present in the tunica adventitia of veins. Additionally, veins possess valves, consisting of intimal folds, which are not present in arteries. Arteries can also be distinguished by their dominant tunica media. 100x

Several criteria distinguish a medium vein from its accompanying medium (muscular) artery. Veins possess wider lumens, thinner walls and more irregular outlines than do arteries; longitudinally-oriented smooth muscle may be present in the tunica adventitia of veins. Additionally, veins possess valves, consisting of intimal folds, which are not present in arteries. Arteries can also be distinguished by their dominant tunica media. 100x

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 primarily by contraction of adjacent skeletal muscle, which produces a milking action in the vein.

Several criteria distinguish a medium vein from its accompanying medium (muscular) artery. Veins possess wider lumens, thinner walls and more irregular outlines than do arteries; longitudinally-oriented smooth muscle may be present in the tunica adventitia of veins. Additionally, veins possess valves, consisting of intimal folds, which are not present in arteries. Arteries can also be distinguished by their dominant tunica media. 100x

Several criteria distinguish a medium vein from its accompanying medium (muscular) artery. Veins possess wider lumens, thinner walls and more irregular outlines than do arteries; longitudinally-oriented smooth muscle may be present in the tunica adventitia of veins. Additionally, veins possess valves, consisting of intimal folds, which are not present in arteries. Arteries can also be distinguished by their dominant tunica media. 100x

The enclosed area is shown in the next image.