What type of layer do capillaries possess that is continuous with arteries and veins?

Capillaries possess a layer of endothelium, which is a thin layer made up of endothelial cells. This layer is crucial as it forms the innermost lining of blood vessels, including arteries and veins, ensuring a continuous structure throughout the circulatory system. The endothelium serves several functions, such as acting as a barrier between the blood and surrounding tissues, facilitating the exchange of oxygen, carbon dioxide, nutrients, and waste products between the blood and the tissues.

While other layers may be present in larger blood vessels (like the fibrous tissue that provides structural support in arteries and veins, or muscle layers that enable contraction and expansion), capillaries solely consist of this single layer of endothelial cells. This unique structure is what allows for their primary function—efficient exchange of materials at the cellular level. Thus, identifying the type of layer present in capillaries as endothelium provides insight into both their structure and function within the cardiovascular system.