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 also any type of clinical connections pertaining to them.

You are watching: Which of the following is the outermost covering of the heart?

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

Recalling from the heart anatomy, it has actually 2 atria and also two ventricles that consist of facets and necessary procedures for the heart cycle. But let’s take a look at the heart histology; it is necessary for understanding the function of the heart. Histologically, the heart is made of three layers of tissue: epicardium, myocardium, and also endocardium.

Key facts about 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 valvesComprised of a layer of endothelial cells, and also a layer of subendocardial connective tissue
Clinical relationEndocarditis

Contents
+ Show all

Epicardium


*
*

The epicardium is the outermany 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 exact same as the parietal pericardium. 

Below the mesothelial cells is a layer of adipose and connective tconcern that binds the epicardium to the myocardium and also cushions the heart. Nerves and also blood vessels that supply the heart are discovered in the epicardium. At the roots of great vessels, the epicardium mirrors back and continues as the parietal pericardium, forming an enclosed pericardial sac. The sac is filled via serous pericardial liquid that stays clear of friction during heart contractions.

Once you"ve finiburned learning about the layers of the heart, start examining the main frameworks of the heart with our handy diagrams, worksheets and also quizzes

Myocardium


*
*
*

The myocardium is functionally the major constituent of the heart and also the thickest layer of all 3 heart layers. It is a muscle layer that enables heart contractions. Histologically, the myocardium is consisted of 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 dispersed in the perimeter of the cell.

Cardiomyocytes are incredibly well-off in glycogen deposits and mitochondria. This has a good sensible meaning given that the myocardium is constantly contracting and needs an excellent amount of energy at all times. Cardiomyocytes also contain yellow lipofuscin granules. They don’t have actually any kind of particular sensible significance, yet they are interesting since they are age markers for the cell. The older the cell, the even more lipofuscin it has actually. 

Cardiomyocytes connect through one-of-a-kind intercellular bridges called intercalated discs. The discs consist of of 3 components: adherens junction (fascia adherens), desmosomes (maculae adherentes) and gap junctions (connecting junctions). These 3 components allow mechanical unity of cardiomyocytes and also a straight pathway of spreading action potentials. Thus, the myocardium is observed as a form of syncytium, quite than a group of rather independent cells.


Although the structure of myocardium is the very same in the atria and also ventricles, it is thicker in the ventricles. This is due to the higher hydrostatic pressure that the ventricles need to get rid of when pumping the blood right into the systemic vessels. 

Endocardium

The endocardium is the innermost layer of the heart. It lines the inner surencounters of the heart chambers, consisting of the heart valves. The endocardium has 2 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 constant via the connective tconcern of the myocardium. Branches of the heart’s conduction mechanism are immersed into the subendocardial layer.

Solidify your knowledge through our quiz:


Clinical relations: Endocarditis

Endocarditis is an inflammation of the endocardium. Normally, it has actually an transmittable etiology. It mainly affects currently damaged heart valves and in the majority of cases, is caused by the bacteria Streptococcus viridans. In the case of a healthy and balanced heart, the pathogenic bacteria is Streptococcus aureus. No issue what bacteria is the cause, pathogenesis is the exact same. Once the bacteria lugged by the bloodstream reaches the heart valves, they attack the endocardium. Then they cause the destruction of heart tworry, which leads to the formation of friable vegetations composed of necrotic debris (destructed heart cells), thrombi, and also microorganisms. Parts of the vegetation have the right to be loosened by the bloodstream and also disseminated throughout the body, creating second deposits of infection. If the bring about bacteria is incredibly virulent, the endocarditis has actually a fulminant course and frequently a fatal outcome. On the various other hand also, when the bacteria are not so virulent they can persist for some time in the heart bring about valves deformities. 

It is exciting that Streptococcus viridans is typically found in the dental cavity, wbelow the most basic way for it to reach the heart and also form vegetations on damaged valves is during a stomathology procedure. For this factor, it is vital to indevelop your medical professional if you have actually a valve problem, so they can prescribe antibiotics for precautions. 

Usual symptoms of endocarditis are flu-prefer indications, heart murmur, night sweating, shortness of breath, and chest pain throughout breathing. Infectious endocarditis is treated by intravenous antibiotics for 2 to 6 weeks. If the disease has actually substantially damaged the heart valves, it is shown to perform a valve replacement or repair surgical procedure. 


Layers of the heart: desire to learn more around it?

Our engaging videos, interenergetic quizzes, detailed short articles and HD atlas are below to obtain you top outcomes quicker.

See more: Why Is There A Large Increase Between The First And Second Ionization Energies Of The Alkali Metals

What do you favor to learn with?


“I would certainly honestly say that nlinux.org cut my examine time in fifty percent.”–Read more.

*
Kim Bengochea, Regis College, Denver


References: