Comprises three layers
- Endocardium, Myocardium, Epicardium
- Innermost layer of endothelial cells.
- Its function is to line the chambers and valves of the heart, creating a smooth surface to reduce friction with the blood.
- Site of endocarditis
- Muscle cells contract to pump blood from the heart; are arranged in bundles wrapped in connective tissue.
- Myoendocrine cells that produce atrial natriuretic peptide (aka, factor or hormone) in response to high blood pressure.
- Nodal cardiocytes control the rhythmic contraction of the myocardium (these cells are concentrated in the sinoatrial and atrioventricular nodes).
Details of cardiac muscle cells:
- Have 1-2 centrally located nuclei.
- Cells branch to connect with multiple adjacent cells.
This arrangement increases intercellular connections, which are marked by intercalated discs, for efficient signal conduction.
- Intercalated discs comprise interdigitating processes that hold adjacent cells together via complex junctions to rapidly spread contraction signals throughout the myocardium.
- Purkinje fibers
Are lighter in the center and lie nearer the endocardium than do muscle cells
Purkinje fibers are part of conduction system of the heart.
- Contributes to the serous layer of the pericardium, the protective sac that envelops the heart.
- Comprises simple squamous epithelium.
- Subepicardial connective tissue comprises adipose and other connective tissues, passage for coronary blood vessels and nerves.