What are the distinguishing features that can be observed under a microscope to differentiate between an artery and a vein?

Under a microscope, arteries and veins can be differentiated by their distinct features. Arteries typically have thicker walls and a smaller lumen compared to veins. Arteries also have more elastic fibers in their walls, allowing them to withstand high pressure. Veins, on the other hand, have thinner walls and a larger lumen to accommodate the lower pressure of blood flow. Additionally, veins often have valves to prevent backflow of blood, which arteries do not have. These differences in structure can help identify whether a blood vessel is an artery or a vein when viewed under a microscope.