Collagen, a major protein of the white fibers of connective tissue, cartilage, and bone, resists stretching and thereby prevents overdistension of the vasculature. Smooth muscle provides the contracting component of the vascular system that regulates vasoconstriction and dilation. Elastic arteries contain large amounts of elastic tissue, which enables them to distend and recoil during systole and diastole to help propel blood. The muscular arteries mainly comprise smooth muscle cells and control blood flow to the periphery and major organs. These arteries are capable of constricting and dilating to allot varying degrees of blood flow to certain tissues according to their needs.
Muscular arteries are major regulators of systemic blood pressure.
These changes result in increased arterial rigidity, elongation, and tortuousity. Arterioles, the populous branches of small arteries, become progressively fibrotic and thicken with age. The atherosclerotic process occurs in vessels of the heart, brain, and kidneys, while peripheral arterial disease creates problems in the extremities. The disease is asymptomatic until approximately 70 percent of the vessel lumen becomes occluded. The resulting decrease in blood flow leads to tissue ischemia and increases the risk of thrombi formation, which can result in severe ischemia and possibly gangrene.