The tissue shown in the image is a section of which structure?

• A. Muscular artery
• B. Vein
• C. Nerve
• D. Lymph node

Answer: (A)

Muscular arteries have a thick tunica media made of multiple concentric smooth muscle layers, with a distinct internal elastic lamina separating the intima from the media. In tissue sections, this gives a relatively small, round lumen surrounded by a well-defined, muscular wall and a dark, wavy line (the internal elastic lamina) at the inner border of the media. The adventitia sits outside and may contain small vessels (vasa vasorum). These features distinguish a muscular artery from veins, which have thinner walls and larger, more collapsible lumens often without a pronounced elastic lamina, from nerves (bundles of nerve fibers with protective coverings) or lymph nodes (nodal cortex, germinal centers, and distinct architecture). Therefore, the structure shown is a muscular artery.