Endocardium: What is it? Types of Layers, Functions and Associated Conditions

It is the thin inner layer of the heart wall.

This layer covers the internal chambers of the heart, protects the valves of the heart, and is continuous with the endothelium of the great blood vessels. The endocardium of the atrium of the soul consists of smooth muscle and elastic fibers.

Now, the heart has some different coatings associated with it, so to better understand where the endocardium is, let us make a quick review of the heart’s anatomy.

The heart is part of the cardiovascular system. The cardiovascular system, sometimes called the circulatory system, comprises the heart and arteries, veins, and capillaries that extend throughout the body.

The outer part of the heart is lined with a thin tissue called the pericardium. Below the pericardium, you have the fibrous pericardium and the serous pericardium.

Beneath the serous pericardium is the epicardium. Below the epicardium, there is a thick muscular layer called the myocardium. Then, finally, we reach the thin inner layer of the heart, which is the endocardium.

Endocardium layers

The endocardium covers both the atria, the ventricles, and heart valves. This thin and delicate lining of the heart is composed of three layers:


Connective subendocardial tissue:

The first layer contains the connective tissue and the Purkinje fibers. The Purkinje fibers help conduct electricity through the cardiac muscle, and the connective tissue helps the endocardium attach to the myocardium.

Fibro-elastic tissue:

The second layer contains a thin muscular layer and has more connective tissue, so it is thickest in the atria than in the ventricles.

Fibers of collagen, elastic tissue, and some smooth muscle are the components of this layer.


The third layer contains vascular endothelium formed by special cells that line the inside of the circulatory system.


This thin but important layer fulfills three fundamental functions in the cardiovascular system.

1) The endocardium is responsible for the blood flowing freely throughout the tissues, as it provides a smooth surface for the interior of the heart.

Thanks to the endocardium, the blood components do not adhere to the heart’s walls; if this happens, it could cause tissue damage or induce blockages. This membrane also helps prevent the heart tissues from sticking when they beat.

2) The endocardium is essential for the heart to beat by containing the Purkinje fibers.

The Park fibers transmit the electrical signals to the whole heart. This electricity, in turn, helps the heart muscles contract.

3) The endocardium has additional layers around the heart’s valves (atrioventricular and semilunar), which join with the valves to make them stronger and work better.

Symptoms in the endocardium

The endocardium is vulnerable to rheumatic heart disease and valvular heart disease damage. These conditions can cause irritation that inflames the endocardium. An infection of the endocardium can lead to a condition known as endocarditis.

Endocarditis is typically the result of infection of the heart valves or the endocardium by certain bacteria, fungi, or other microbes. Endocarditis is a severe disease that can be fatal.

Valvular disease:

Diseases of the heart’s valves take two varieties of names, one that refers to the name of the valves affected and the other to the nature of the disease.

About the valves themselves, there are said to be four varieties of diseases, namely:

Aortic disease: Insufficiency of the semilunar or aortic valves; the valves that lie between the aorta, the sizeable outgoing artery, the left ventricle, or the sizeable forced structure of the heart.

Mitral disease: Large bicuspid or mitral valve disease; the valve between the left atrium and the heart’s left ventricle.

Pulmonary valvular disease: Insufficiency of small semilunar or pneumonic valves; the valves between the pulmonary artery, the artery that goes to the lungs from the right ventricle of the heart and the right ventricle.

Tricuspid disease: Difference of the tricuspid valve, the valve between the right atrium and the heart’s right ventricle.

Of these valvular structures, the valves on the left side of the heart, the aorta, and the mitral valve are much more prone to disease than the valves, pulmonary and tricuspid, on the right side.

It can be said that valvular disease on the right side is relatively rare. I have tried to explain in my experimental research on “the synthesis of valvular disease” by showing that the valvular disease is due to irritation in most cases.

Valvular diseases are, by far, the most prevalent in people of the rheumatic constitution and are the frequent consequences of acute rheumatic fever.

Divided according to the nature of the disease, valvular heart conditions are:

Vegetations: Small growths, similar to fungoid vegetations, occur at the margins or thin surfaces of the valves.

Thickening: The fibrous tissue of the valvular structure thickens and condenses so that the valves do not act with due ease of opening and closing for the admission or stoppage of the blood flow.

Fat and calcareous degenerations: Fat degeneration is called atheroma, and calcaneus is called ossification.

They consist of changes in which the valve structures are transformed, in part, into a form of a fatty system or a bone substance and in which the regulating movements of the valves are highly impeded.

Aneurysm Disease that consists of enlargement, dilatation of the valves, or growth of the vessels through which blood is supplied to the valves.

Laceration:  Accidental tearing of the valvular structure under great excitement or tension. In sporadic cases, this accident has occurred where there has been a very healthy valve condition.

Dilatation of the orifice of the valves: A condition in which the opening or orifice of the valves is very dilated so that the curtains of the valves that leave the orifice become Inca to fulfill perfectly in the act of closing.

This condition is common in cases where the heart is subjected for many years to severe stress due to extreme action and where all its structures are dilated.

In certain of these forms of valvular disease, regurgitation of the blood is not often detected by the physician.

The term means that, due to the imperfect action of the valves, they do not close efficiently, so that the blood they must prevent from returning and that they must direct in their course flows backward or regurgitates in the cavity from which it originates.