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Cross section of vein

Arteries and veins have the same layers of tissues in their walls, but the proportions of these layers differ. A cross section of a vein displays its layered structure, including the tunica externa, tunica media, and tunica intima. The tunica intima contains an endothelial lining and valves to ensure one-way blood flow. Veins have a larger lumen and flattened appearance. This structure facilitates the return of deoxygenated blood to the heart in the circulatory system.