THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -The muscle layer of the heart is termed the myocardium and is made up of cardiomyocytes. The myocardium is found in the walls of all four chambers of the heart, though it is thicker in the ventricles and thinner in the atria.

Detailed explanation-2: -Cardiac muscle contraction is an electrical event initiated at the sinoatrial node. Each cardiac muscle cell fires an action potential as a result of excitation propagated from the sinoatrial node, which produces muscle cell contraction.

Detailed explanation-3: -The myocardial layer contains the contractile elements of the heart. The bundles of striated muscle fibres present in the myocardium are arranged in a branching pattern and produce a wringing type of movement that efficiently squeezes blood from the heart with each beat.

Detailed explanation-4: -The epicardium is the outer layer that contains blood vessels. The myocardium is the middle layer that is composed of contractile tissues. The endocardium is the innermost layer and composes the valves, inner lining of the chambers, and contains vessels and nerves.