cardiomyocyten

Cardiomyocytes are the muscle cells that make up the heart muscle, or myocardium. They are specialized for contraction and provide the force that pumps blood through the circulatory system. Cardiomyocytes are connected end-to-end by intercalated discs, which contain desmosomes and gap junctions to synchronize electrical activity and mechanical force across the heart.

Structurally, cardiomyocytes are elongated, branched cells with a typically single nucleus (though bi- or occasionally multinucleated forms can occur). They are striated due to orderly sarcomeres and contain a high density of mitochondria to support their energy demands. Intercalated discs link neighboring cells, enabling rapid cell-to-cell conduction of impulses via gap junctions and ensuring mechanical continuity through desmosomes. They also possess transverse tubules and a well-developed sarcoplasmic reticulum for calcium handling.

Excitation-contraction coupling in cardiomyocytes relies on calcium ions released from the sarcoplasmic reticulum, with calcium influx triggering actin–myosin cross-bridge cycling. Cardiomyocytes depend largely on oxidative metabolism and fatty acids for energy, supported by their abundant mitochondria. They have limited glycolytic capacity relative to some other cell types and are highly sensitive to changes in oxygen supply.

Physiologically, the heart’s rhythmic activity arises from the intrinsic conduction system, modulated by autonomic input, while individual cardiomyocytes respond to pacing and mechanical load. In adulthood, regenerative capacity is limited; after injury such as myocardial infarction, lost cardiomyocytes are typically replaced by scar tissue rather than new myocytes, which can impair function. Chronic stress can induce hypertrophy and remodeling of cardiomyocytes, contributing to cardiomyopathy and heart failure if maladaptive.