Endocardium: definition, location and function


The endocardium is a thin, smooth tissue that forms the lining of the heart's chambers and valves . The innermost layer of the heart's walls, it serves as a barrier between the heart muscles and the bloodstream and contains the necessary blood vessels. It also contains the heart's conduction system , which regulates the activity of the heart muscles.

Given this vital role, both in conducting blood through the heart and regulating heart rate, problems in the endocardium can have serious health consequences. The most notable of these is endocarditis , an infection and inflammation of these tissues, which especially affects the valves .

Let's take a quick look at the anatomy and function of the endocardium and how it relates to health problems.

Definition and function

The heart, which carries blood throughout the body, consists of four chambers lined with endocardium. As the innermost layer of the heart's walls, it serves two important functions :

  • Anatomical function : The tissue that lines the inside of the heart, the endocardium, maintains blood flow through the heart separate from the myocardium or the heart muscles. It also covers the valves that open and close to regulate blood flow in the chambers of the heart.
  • Conduction System : Heart rate and activity are regulated by electrical signals that travel through nerves embedded in the endocardium. These nerves are connected to the myocardium, which causes the muscle to contract and relax, pumping blood through the body.


In addition to what it does, it is also important to understand the location and structure of the endocardium.


As the inner lining of the heart, the endocardium is located along the walls of the four chambers of the heart (the left and right ventricles and the left and right atria). In addition, this tissue is the outer layer of the tricuspid, pulmonary, mitral, and aortic valves, which serve as the entry gate between the chambers .

The endocardium is one of the three layers that make up the walls of the heart. As the innermost of these, it is associated with the myocardium, which is the thickest of the layers and is made up of the muscles of the heart. The myocardium surrounds the epicardium, the tissue that contains the primary nerves, blood vessels, and arteries that serve the heart .


The endocardium consists of three sublayers that define its function. Are:

  • The endothelium is the innermost layer that controls the exchange of any material between the bloodstream and the muscles of the heart. It consists of specialized endothelial cells that line arteries and veins of the same type.
  • The elastic tissue layer is made up of smooth muscle, which exerts pressure on the veins running through the layer and on the connective tissue .
  • The subendocardial layer is the outermost sublayer of the endocardium, serving as connective tissue with the heart muscle. Along with nerves and blood vessels, it contains fibrous collagen cells, which provide structure and stability, and Purkinje fibers, which send electrical signals to the myocardium .

Related conditions

Given its central role in the heart, the condition of the endocardium can have serious consequences.


Endocarditis is an infection and inflammation of the endocardium. This is the most important and common endocardial disease. As a summary:

  • Symptoms : Endocarditis causes a number of symptoms, including fever, chills, fatigue, chest pain, swelling of the extremities or abdomen, night sweats, and muscle and joint pain. If this box is unchecked, the broader health effects are visible.
  • Causes : This condition is usually caused by a bacterial infection (called infective endocarditis), although it can occur for other reasons as well.
  • Diagnosis : If suspected, doctors diagnose the condition by performing blood tests along with images of the heart, such as an echocardiogram , magnetic resonance imaging (MRI) , and cardiac angiography , among others.
  • Treatment : Antibiotics given intravenously (through an IV) are the first line of treatment, although surgery can be done if they don't work. The latter involves careful removal of infected endocardial tissue, drainage of inflamed areas, and, if necessary, repair and / or replacement of affected tissue .
  • Forecast : The condition, which usually occurs when patients have other heart problems or artificial valves, the prognosis for endocarditis is relatively poor: 10 to 26% of patients experience in-hospital mortality and an estimated 60 to 70% survive five years after. This condition is strongly influenced by the age of the patient, as well as his medical history.

Mitral valve prolapse (MVP)

This congenital condition is characterized by abnormally thick tissue (including the endocardium) in the mitral valve (between the left ventricle and the atrium). MVP pushes the valve back into the left atrium, causing blood to flow back.

Generally asymptomatic, it can be characterized by sudden increases in heart rate, fatigue, and chest discomfort. This is detected by imaging techniques such as an echocardiogram (echo). Treatment is usually not required; however, progressing to the point where the valve leaks requires intervention to prevent a stroke or heart attack .

Carcinoid heart disease

Sometimes called "Headinger syndrome": it is the development of carcinoid syndrome , a spectrum of disorders that arise from the excessive secretion of hormones. Thus, symptoms include facial flushing, chronic diarrhea, hypotension (low blood pressure), and others.

Ultimately, this can lead to right ventricular failure, causing shortness of breath, fatigue, leg swelling, fast and irregular heartbeat, and rapid weight fluctuations. Diagnosis is made using standard cardiac imaging techniques, such as the electrocardiogram (ECG), computed tomography (CT), and others. It can be treated with medication or by surgically removing problem tissues .

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