What is the endocardium?
What is the endocardium? The heart’s endocardium is a smooth tissue layer that lines its chambers. One of three layers making up the heart wall, the thin membrane covers the left atrium, the right atrium, the left ventricle, and the right ventricle.
In addition to lining the atria and the ventricles, the endocardium covers and forms the surface of the four heart valves. The valves of the heart are the mitral (bicuspid) valve, the aortic valve, the tricuspid valve, and the pulmonary (pulmonic) valve.
The other two heart wall layers are the myocardium and the epicardium. The myocardium is the middle layer, which is made up of cardiac muscle that enables the heart to contract. The epicardium is the outer layer. It protects the heart’s inside layers and aids in making pericardial fluid. The epicardium is also called the visceral pericardium because it forms the pericardium’s innermost layer.
What does the endocardium look like?
So, what is the endocardium and what does it look like? It is a delicate, translucent tissue layer with a composition that is structurally similar to the endothelium that lines the interior surface of blood vessels. As mentioned above, the membrane is smooth and thin, covering the chambers and valves of the heart. However, the structure of the tissue varies depending on the region of coverage.
For example, the endocardium is thicker in the atria than it is in the ventricles. It also tends to be thicker on the left side of the heart and in the ventricular outflow tracts. Both ventricular endocardium and atrial endocardium consist of layers that contain elastic fibers and muscle tissue, as well as connective tissue. Just below the endocardium are specialized fibers known as Purkinje fibers.
The Purkinje fibers, which are separated by collagen and the fibrous skeleton of the heart, are located in the subendocardium, within the walls of the ventricular chambers. They cause the left and right ventricles to contract in synchronization to maintain a consistent heart rhythm. An accumulation of fat called pericardial adipose tissue encases the three purposeful layers of the heart wall.
What is the function of the endocardium?
In heart anatomy and physiology, the endocardium is a necessary component with several functions. Firstly, its smooth surface makes it possible for blood cells and platelets to flow freely through the heart without adhering to the heart’s walls, preventing damage and blockages. The endocardial lining also prevents heart tissues from sticking to each other during the cardiac cycle.
For people researching what is the endocardium, another key endocardium function is to support the subendocardial layer that houses the Purkinje fibers. During systole, these cardiac fibers transmit contraction impulses to the myocardium of the left and right ventricles. As a result, the muscle tissue of the ventricles contracts, generating sufficient force to expel blood from the heart.
Finally, the endocardium enhances heart function by strengthening vital heart structures, specifically the valves. The heart’s valves regulate blood flow so that blood can travel through the heart at the correct rate in one direction. By forming additional folds around these regulators, the endocardium provides added support that strengthens the valves and enables them to work optimally.
What can go wrong with the endocardium?
Various issues can affect the endocardium. Endocardial tissue can become thickened, scarred, and/or damaged, or there may be tissue death. This can lead to dysfunction of the heart. In children, thickening can result from endocardial fibroelastosis and endomyocardial fibrosis. In adults, congenital heart disease, carcinoid syndrome, and myocardial infarctions are possible causes.
When a myocardial infarction occurs, ischemia of the myocardium can extend to the endocardium and create areas of dead tissue. The dead tissue can accompany scarring or damage, affecting how the heart contracts and relaxes during the cardiac cycle and producing dangerous abnormal heart rhythms. It also increases the risk of ruptures and blood clotting, which can be life threatening.
Infective endocarditis is another serious problem that can affect the endocardium. This is an infection that causes abnormal growths (vegetations) to form on the endocardium’s surface or in the endocardium itself. It usually involves the heart valves but can affect the lining of the chambers and other structures. Complications include heart valve insufficiency, heart failure, and strokes.