How do veins and arteries differ in their structure? The answer to this question is most directly dictated by the function of these vessels. Arteries need to resist the high pressure inside the vessel - the heart tries to "push out" the blood with the greatest force. Therefore, arteries have an elastic sheath, which keeps them in shape. Besides, this type of vessels has to change their lumen in order to vary the level of blood flow. Therefore, they have a well-developed layer of muscle tissue. As a result, arteries are much thicker. But the veins themselves are pliable and inelastic, as they do not have such properties☝🏻 Although some of them (veins of the lower extremities) have another unique property - they have valves that prevent the backflow of blood.