Author: Jana Vasković•Reviewer: Dimitrios Mytilinaios MD, PhDLast reviewed: May 31, 2021Reading time: 6 minutes


This article will certainly talk about the layers of the heart (the epicardium, the myocardium and the endocardium) and any clinical relationships pertaining to them.

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In the exact same way that vehicles have actually their fuel pumps, our body has actually the heart. The heart is a muscular body organ discovered in the middle mediastinum that pumps blood throughout the body. It is hooffered in the pericardial sac, which protects it and also assists via its mechanics.

Recalling from the heart anatomy, it has 2 atria and 2 ventricles that make up aspects and important procedures for the heart cycle. But let’s take a look at the heart histology; it is important for knowledge the function of the heart. Histologically, the heart is made of 3 layers of tissue: epicardium, myocardium, and also endocardium.

Key facts around the layers of the heart
EpicardiumVisceral layer of serous pericardiumComprised of mesothelial cells and also fat and connective tissues
MyocardiumMuscle layerComprised of cardiomyocytes
EndocardiumLines inner surface of heart chambers and also valvesComprised of a layer of endothelial cells, and also a layer of subendocardial connective tissue
Clinical relationEndocarditis

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The epicardium is the outera lot of layer of the heart. It is actually the visceral layer of the serous pericardium, which adheres to the myocardium of the heart. Histologically, it is made of mesothelial cells, the same as the parietal pericardium. 

Below the mesothelial cells is a layer of adipose and connective tworry that binds the epicardium to the myocardium and cushions the heart. Nerves and blood vessels that supply the heart are uncovered in the epicardium. At the roots of good vessels, the epicardium reflects ago and also continues as the parietal pericardium, forming an enclosed pericardial sac. The sac is filled with serous pericardial liquid that prevents friction during heart contractions.

Once you"ve finiburned finding out about the layers of the heart, begin examining the major frameworks of the heart via our handy diagrams, worksheets and also quizzes



The myocardium is functionally the major constituent of the heart and the thickest layer of all three heart layers. It is a muscle layer that permits heart contractions. Histologically, the myocardium is comprised of cardiomyocytes. Cardiomyocytes have a single nucleus in the center of the cell, which helps to distinguish them from skeletal muscle cells that have actually multiple nuclei distributed in the periphery of the cell.

Cardiomyocytes are extremely rich in glycogen deposits and mitochondria. This has actually an excellent useful meaning given that the myocardium is constantly contracting and also demands an excellent amount of energy at all times. Cardiomyocytes also contain yellow lipofuscin granules. They don’t have any type of specific useful definition, but they are exciting given that they are age markers for the cell. The older the cell, the more lipofuscin it has. 

Cardiomyocytes connect via special intercellular bridges called intercalated discs. The discs consist of of three components: adherens junction (fascia adherens), desmosomes (maculae adherentes) and gap junctions (connecting junctions). These three components enable mechanical unity of cardiomyocytes and also a straight pathway of spreading action potentials. Because of this, the myocardium is oboffered as a kind of syncytium, fairly than a group of rather independent cells.

Although the structure of myocardium is the exact same in the atria and ventricles, it is thicker in the ventricles. This is due to the better hydrostatic press that the ventricles should conquer when pumping the blood into the systemic vessels. 


The endocardium is the innermany layer of the heart. It lines the inner surdeals with of the heart chambers, including the heart valves. The endocardium has actually two layers. The inner layer lines the heart chambers and is made of endothelial cells. Superiorly, is the second layer: a subendocardial connective tissue which is consistent via the connective tissue of the myocardium. Branches of the heart’s conduction system are immersed into the subendocardial layer.

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Clinical relations: Endocarditis

Endocarditis is an inflammation of the endocardium. Usually, it has actually an infectious etiology. It greatly affects already damaged heart valves and also in many cases, is caused by the bacteria Streptococcus viridans. In the instance of a healthy and balanced heart, the pathogenic bacteria is Streptococcus aureus. No matter what bacteria is the cause, pathogenesis is the very same. Once the bacteria brought by the bloodstream reaches the heart valves, they attack the endocardium. Then they reason the damage of heart tconcern, which leads to the formation of friable vegetations created of necrotic debris (destructed heart cells), thrombi, and also microorganisms. Parts of the vegetation can be loosened by the bloodstream and disseminated throughout the body, forming additional deposits of infection. If the bring about bacteria is extremely virulent, the endocarditis has a fulminant course and also frequently a fatal outcome. On the other hand, when the bacteria are not so virulent they have the right to persist for some time in the heart bring about valves deformities. 

It is exciting that Streptococcus viridans is generally discovered in the oral cavity, wright here the simplest method for it to reach the heart and also develop vegetations on damaged valves is throughout a stomathology procedure. For this factor, it is crucial to indevelop your medical professional if you have actually a valve trouble, so they could prescribe antibiotics for preadvises. 

Usual symptoms of endocarditis are flu-prefer indications, heart murmur, night sweating, shortness of breath, and chest pain in the time of breapoint. Infectious endocarditis is treated by intravenous antibiotics for 2 to 6 weeks. If the disease has substantially damaged the heart valves, it is suggested to perdevelop a valve replacement or repair surgery. 

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