Endocardium

• Innermost layer of heart wall
• Endocarditis (inflammation of the endocardium) can destroy the valves and disrupt blood flow through the heart.

Myocardium

• Cardiac muscle fibers (cells) are anchored to the dense regular connective tissue of the fibrous skeleton. In addition to anchoring the cardiac muscle fibers, the fibrous skeleton maintains the structural and physiological integrity of the heart.
• The myocardial layer is injured in myocardial infarction (aka, heart attack), which occurs when obstructed coronary artery blood flow causes cardiac muscle cell death.

Epicardium

• Most superficial layer of heart wall
• Often filled with fat
• Two sublayers; outermost layer is visceral layer of pericardium.

Pericardium:

Fibrous layer

• Most superficial layer
• Tough layer of dense connective tissue
• Because it is inelastic, it prevents overfilling of the heart.
• Arises from the diaphragm
• Covers the heart and the roots of the great vessels, with which it is continuous

Serous layer

• Parietal layer:
  Lines the fibrous pericardium
• Pericardial cavity
  Between parietal and visceral layers; contains thin layer of fluid to reduce friction and allow movement of heart
• Visceral layer
  Forms most superficial layer of the epicardium

Pericarditis (inflammation of the pericardium) causes the pericardium to rub against the heart, which causes friction. As a result, patients experience pain and can even suffer from impaired heart function, which, sometimes necessitates medical or surgical intervention.