The heart wall is composed of connective tissue, endothelium, and cardiac muscle. It is the cardiac muscle that enables the heart to contract and allows for the synchronization of the heartbeat. The heart wall is divided into three layers: epicardium, myocardium, and endocardium.

Epicardium (epi-cardium) is the outer layer of the heart wall. It is also known as visceral pericardium as it forms the inner layer of the pericardium. The epicardium is composed primarily of loose connective tissue, including elastic fibers and adipose tissue. The epicardium functions to protect the inner heart layers and also assists in the production of pericardial fluid.

Myocardium (myo-cardium) is the middle layer of the heart wall. It is composed of cardiac muscle fibers, which enable heart contractions. The myocardium is the thickest layer of the heart wall, with its thickness varying in different parts of the heart. The myocardium of the left ventricle is the thickest, as this ventricle is responsible for generating the power needed to pump oxygenated blood from the heart to the rest of the body.

Endocardium (endo-cardium) is the thin inner layer of the heart wall. This layer lines the inner heart chambers, covers heart valves, and is continuous with the endothelium of large blood vessels. The endocardium of heart atria consists of smooth muscle, as well as elastic fibers.

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