GROSS ANATOMY

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: -The heart consists mostly of cardiac muscle cells (or myocardium). The outstanding characteristics of the action of the heart are its contractility, which is the basis for its pumping action, and the rhythmicity of the contraction.

Detailed explanation-3: -Detailed Solution. The correct answer is Muscular tissue. The heart is made up of a special type of muscle tissue termed cardiac tissue.