Define any structural difference between arteries …

Arteries are thick where as veins are thin

STRUCTURE OF ARTERIES AND VEINS Arteries carry blood away from the heart, and veins carry blood toward the heart, but that is not the only difference. Arteries and veins differ in their structure as well. If an artery is compared to a coresponding vein the size of the artery would be smaller, its lumen would be smaller, the wall would be thicker. The inner lining of an artery is typically wrinkled due to the contracted state of the smooth muscle in the artery wall. Veins have a relatively thin layer of smooth muscle in the wall, and often the veins have a misshapen or collapsed look, whereas arteries maintain a tight cylindrical shape.  Veins also have valve flaps to keep the blood from moving backward in the vessel. These valves resemble the semilunar valves of the heart.    Arteries and veins are similar in that the layers which form the walls are similar in composition. The innermost layer is the tunica intima. The tunica intima consists of an epithelial lining of simple squamous cells (endothelium), a basal lamina, and some supporting connective tissue. In arteries there is an internal elastic membrane where the tunica intima layer meets the tunica media layer. The tunica media is comprised mostly of smooth muscle. In large arteries the tunica media has an abundance of elastic fibers in addition to the smooth muscle. In small veins and capillaries the tunica media is absent. The third and outermost layer of a vessel is the tunica adventitia. This layer is made of connective tissues, which, in turn, form a loose attachment to surrounding tissues. The tunica adventitia is relatively thick in larger veins and may contain a considerable amount of elastic fiber.                                     STUDY TOPICS IN SEQUENCE Introduction to the Circulatory System The Human Heart Major Systemic Vessels Arteries and Veins Heart Development Vertebrate Hearts Things To Know List