What are the three main components of vein walls?

The three main components of vein walls are correctly identified as the adventitia, media, and intima.

The adventitia, or tunica externa, is the outermost layer and is composed primarily of connective tissue, which provides structural support and flexibility to the vein. The media, or tunica media, is the middle layer and consists mainly of smooth muscle and elastic fibers, allowing the vessel to expand and contract as needed to accommodate varying volumes of blood. The intima, or tunica intima, is the innermost layer, primarily made up of endothelial cells that line the lumen of the vein, facilitating smooth blood flow and acting as a barrier to prevent thrombosis.

While the other options mention components or concepts related to veins, they do not accurately describe the three main structural components of vein walls as classified in vascular biology. Understanding the anatomy of vein walls is crucial for a phlebology sonographer, as it aids in recognizing normal physiological function and potential pathological changes that may occur in venous systems.