Architecture of the Blood Vessels

Abstract

The blood vessels are tubular structured consisting of three layers: the tunica intima, the tunica media, and the tunica adventitia. The tunica intima is the innermost layer of the vessels mainly made up by one layer of endothelial cells. With the exception that the capillaries have only the tunica intima, the arteries and veins also possess the other two layers. The tunica media, i.e., the middle layer, is constituted of smooth muscle cells, elastic, and collagenous fibrils, while the tunica adventitia is the outermost layer of the vessel wall consisting of dense fibroelastic tissue. The mixtures of different tissue components including smooth muscle, elastic, and collagen fibers as well as the diameter and thickness of the vascular wall vary among different vessel types to serve their functions. In this chapter, the architectural characteristics of the arteries, capillaries, and veins will be discussed. Furthermore, the gap junctions that form intercellular connections and the vessels that provide nutrient to vessel walls as well as some cell types of functional importance including fibroblasts, stem/progenitor cells, and perivascular adipose tissue will be reviewed.