Figure 2.

a) Schematic anatomy of blood vessels at hierarchical length scales. The vascular walls of the aorta and vena cava comprise three concentric layers termed the intima, media, and adventitia, respectively. The capillary wall usually contains a single layer of the intima. In some tissues, such as the lung alveoli and renal nephron, blood capillary is often accompanied by the epithelium. b) Schematic longitudinal cross-sections of healthy and pathological vascular walls, such as aneurysms (saccular and fusiform), atherosclerosis, and hemorrhage.