Which layer of the aorta contains elastic fibers that help dampen the pulse wave?

• A. The tunica media
• B. The tunica adventitia
• C. The tunica intima
• D. The endothelium

Answer: (A)

Elastic fibers in the tunica media—the middle, elastic-rich layer of the aorta—give the vessel its stretch-and-recoil quality. As the heart ejects blood, the elastic lamellae in this layer stretch to store energy. Then, during diastole, they recoil, releasing that energy and helping to push blood forward. This Windkessel effect smooths out the pulse wave, reducing the sharpness of the pressure peak and maintaining more continuous flow downstream. The other layers serve different roles: the tunica intima lines the lumen with endothelium and subendothelial tissue, while the tunica adventitia provides outer structural support and houses vessels and nerves; the endothelium itself is the inner lining and not the primary dampener of pulse waves.