Heart wall:
Endocardium
- Innermost layer of heart wall.
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.
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
Lines the fibrous pericardium
Between parietal and visceral layers; contains thin layer of fluid to reduce friction and allow movement of heart
Forms most superficial layer of the epicardium
Illustrations:
External Heart
Internal Heart
Layers of the Heart Wall
Histology
Photo credits: https://sites.google.com/a/umich.edu/bluelink/resources/bluelinks/unlabeled-heart-images