How many layers do venules typically have?

Venules typically have three layers, which consist of the tunica intima, tunica media, and tunica externa. The innermost layer, the tunica intima, is composed of endothelial cells that provide a smooth surface to facilitate blood flow. The tunica media, the middle layer, is much thinner in venules compared to arteries, consisting of a few smooth muscle cells and elastic fibers. Finally, the outermost layer, the tunica externa, primarily consists of connective tissue that provides structural support and stability to the vessel. This three-layer structure distinguishes venules from capillaries, which have only one layer, and from larger arteries that may have more complex layers. Understanding the structure of venules is important in phlebotomy, as it informs the technician about the characteristics of the venous system and how to avoid complications during blood collection.