The Layers of the Heart and Heart Attacks

There are three layers of tissue in the heart; the epicardium, the endocardium, and the myocardium.

The epicardium is also called the visceral pericardium and is a thin membrane forming the smooth outer surface of the heart (‘peri’ = around, and ‘cardium’ = heart).

The endocardium is the inner lining of the heart (‘endo’= within) and allows blood to move easily throughout the heart. Each heat valve is formed by a fold of endocardium with connective tissue between the two layers.

The myocardium is essentially the muscle of the heart (‘myo’ = muscle). As you may already be aware, there are three types of muscle – skeletal, smooth (e.g. in intestines) and cardiac. The myocardium is the thick, middle layer of the heart and is composed of cardiac muscle cells. It is responsible for the ability of the heart to contract.

Failure of the heart to contract properly (for various reasons) is termed heart failure. Myocardial infarction is another phrase for ‘heart attack’, as an infarct is dead tissue caused by a sudden insufficiency of arterial blood supply. This can be caused by plaque buildup within the walls of blood vessels.