The collagen matrix of the heart.

Scanning electron microscopy demonstrates an extensive and highly organized network of collagen in the left ventricle of all species examined. This system is arbitrarily divisible into three major components: a collagen weave network that surrounds groups of myocytes; an extensive array of collagen struts measuring 120 to 150 nm in diameter that extend from the basal lamina of a myocyte to the basal laminae of all contiguous myocytes; and an array of similar sized collagen struts that extend from the basal lamina of all capillaries to the basal laminae of all contiguous myocytes. The functions of the individual components of this complicated network are not well-defined. The weave network certainly contributes to the viscous and elastic properties of the heart. Myocyte-to-myocyte struts can prevent slippage of adjacent cells during the cardiac cycle and would ensure equal stretch of adjacent myocytes during diastole. Myocyte to capillary struts may be important in maintaining capillary patency during the early phases of systole. In rats. rabbits and hamsters this entire system is virtually absent at birth and develops rapidly to the adult form by 15 days.