The ultrastructure of Cardiac muscle in health and disease

Abstract

The ultrastructure of the muscle cells of the left ventricular wall of the heart of mammals has been described with respect to the distinct cellular constituents. The sarcolemma has the general features of the surface membranes of cells, but additionally contains specialized junctions. Moreover, invaginations and in-pocketings project inward from the cell surface, retaining luminal continuity with the extracellular fluid. The complexity of the sarcotubular system reveals ultrastructural variations, namely as the network, junctional and corbular sarcoplasmic reticulum, which are involved in Ca 2+ distribution but regulate Ca 2+ storage and release in a different manner. Further ultrastructural investigation combined with chemical dissociation techniques has contributed to our understanding of myocardial contractile function. The ultrastructural details of the cellular organelles and inclusions give insight into how simultaneously a variety of coupled processes evolve in the cardiocytes. In addition, this review deals with the ultrastructural changes occuring during basic pathologic processes affecting the myocardium. Emphasis is placed on the ultrastructural changes observed in distinct cell components of cardiocytes which contribute both to the adaptive response of hypertrophic myocardium and to an increased workload, as well as on the devastating ultrastructural alterations elicited by exposure to hypoxia and some toxic drugs.