THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -The muscles of the heart, termed the myocardium, make up the middle and thickest layer of the heart wall. This layer lies between the single-cell endocardium layer, which lines the inner chambers, and the outer epicardium, which makes up part of the pericardium that surrounds and protects the heart.

Detailed explanation-2: -Cardiac muscle cells are located in the walls of the heart, appear striped (striated), and are under involuntary control. Smooth muscle fibers are located in walls of hollow visceral organs (such as the liver, pancreas, and intestines), except the heart, appear spindle-shaped, and are also under involuntary control.

Detailed explanation-3: -Cardiac muscle (also called heart muscle or myocardium) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that constitutes the main tissue of the wall of the heart.