In veins, which tunic is most prominent?

• A. Tunica media
• B. Tunica adventitia
• C. Tunica intima
• D. None of the above

Answer: (B)

Vessel wall structure reflects pressure and function: arteries need a thick muscular middle layer to regulate high‑pressure blood flow, while veins operate at lower pressure and rely more on a sturdy outer scaffold. In veins, the tunica adventitia—the outermost layer—is typically the thickest tunic. It’s mainly connective tissue that helps anchor the vein to surrounding tissues and, in larger veins, contains vessels (vasa vasorum) that nourish the wall since the surrounding tissues aren’t as easily nourished by the bloodstream. The tunica media in veins is relatively thin because there isn’t a constant need to generate strong, pulsatile contractions. The tunica intima remains the inner lining, but it isn’t the most prominent layer in veins. So the most prominent tunic in veins is the tunica adventitia.