MODULE SUPPLEMENT: CARDIOVASCULAR SYSTEM
The Cardiovascular System

The overall purpose of the cardiovascular system is to carry blood, and thus nutrients and oxygen, to the tissues, and to carry waste products of metabolism to sites for elimination, such as the lungs, liver and kidneys.

Normal functioning of the cardiovascular system depends on the physical properties of the heart and blood vessels; that is, their compliance (distensibility and elasticity) and contractility. These properties are in turn dependent on the structural relationships of the tissues making up the heart and blood vessels--the connective, elastic and muscle tissues. Changes occur in the characteristics of these tissues with age, affecting their function.

Functionally, the major point is that, taken together, the cardiovascular system becomes stiffer and less compliant with age, a process termed "Arteriosclerosis". Larger vessels dilate and elongate. These changes alter the vascular system's ability to adapt to changes in demand related to flow. A number of cellular and tissue level changes contribute to this stiffening. The intima, or inner layer of the vessel wall, appears to be especially affected (Lakatta & Sollott, 2002; Lakatta, 2002a). The media also experiences increases in collagen content and fraying of its elastin (Lakatta, 2002a).

Although these structural changes may be part of "normal" aging, some would not agree that these are inevitable changes, as discussed below. However, these processes can contribute to, or worsen, pathological conditions like hypertension, insufficient perfusion of tissues, and weakening or out pouching of arterial walls (aneurysms).