There are three layers constituting the wall and coverings of the heart, the pericardium, the myocardium and the endocardium. The majority of the anterior surface and approximately half of the posterior surface of the heart is covered by the pericardium. The pericardium is a double walled serous membrane. The outer wall is called the parietal pericardium. The inner layer is called the epicardium or visceral pericardium. Between the epicardium and parietal pericardium is a small space called the pericardial cavity. The pericardial cavity contains a serous fluid that is secreted by the epicardium. The epicardium also serves as the outermost wall of the heart.
The middle and thickest layer of the heart is the myocardium or cardiac muscle. The myocardium of the left ventricular wall is thicker than the myocardium of the right ventricular wall. The myocardium between the two ventricles is called the interventricular septum.
The innermost layer is called the endocardium. The endocardium is a serous membrane that is continuous with the endothelium of the arteries and veins. The endocardium also covers the valves of the heart.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.