Which layer of the arterial wall is the innermost layer?

The innermost layer of the arterial wall is the tunica intima. This layer is crucial as it directly contacts the blood flow within the lumen of the artery. The tunica intima is composed of a thin layer of endothelial cells that provide a smooth surface to reduce friction as blood flows through the vessel. It also plays a role in the regulation of vascular functions, including the response to injury and inflammation.

In contrast, the tunica media, which is the middle layer, primarily consists of smooth muscle and elastic fibers that allow the artery to withstand and regulate the pressure of blood flow. The tunica externa, also known as the tunica adventitia, is the outermost layer made up of connective tissues that provide structural support and protection to the artery. Understanding these layers is key to comprehending how blood vessels function and respond to physiological changes.