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Myocardium n., plural: myocardia Muscular section of the heart located in between the epicardium and also the endocardium Source: amendment by Maria Victoria Gonzaga, chathamtownfc.net.org, from the occupational of Blausen.com employee (2014). “Medical collection of Blausen medical 2014”. WikiJournal of medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. Source, CC through 3.0.


Myocardium Definition

What is the myocardium that the heart? that is the muscular middle layer that the heart that is sandwiched between the epicardium and also endocardium. Periodically it is referred to as the mass that the heart. The myocardium is comprised of two species of cells: cardiac muscle cells (also referred to as heart muscle cells,cardiomyocytes, cardiac myocytes, or cardiac rahbdomyocytes) and also fibroblast.

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The heart is the main circulatory body organ in the human body the circulates the blood transparent the body. The love is situated in a slim fibroelastic, double-layered, fluid-filled sac recognized as “pericardium”. The two layers of the pericardium are the outer fibrous or parietal pericardium and also the inner serous or visceral pericardium.


Myocardium (biology definition): The center layer the the wall of the heart; the muscular substance of the heart situated in the middle, i.e. In between the epicardium and also the endocardium. Etymology: from old Greek mûs (“muscle”) + kardía (“heart”).
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Figure 1: The 3 layers of the heart wall. Source: amendment by Maria Victoria Gonzaga, chathamtownfc.net, from OpenStax College, CC by 3.0.

There space three layers in the walls of the heart namely:

Epicardium: the is the outermost layer of the heart wall. This has mesothelial cell under which room connective and also adipose tissues. This layer additionally constitutes the visceral class of the serous pericardium. Below the epicardium coronary arteries and veins, lymphatic vessels, and also nerves space present. Myocardium: This is the muscle great of the love responsible because that the pumping action of the heart and occupies 95% the the cardiomyocytes mass and is the thickest layer in the love wall. The thickness the the myocardial layer is dependant on the press which is present in each chamber. So, the question arises out of the four chambers of the heart, i m sorry chamber has the thickest myocardium. The myocardial class is thin in the atrium while the myocardium is thickest in the ventricles particularly in the left ventricle. Together a matter of the fact, in adult animals, the left ventricular myocardium is three times thicker than the best ventricular myocardium. This is rather intriguing and instigates the query as to why is the left ventricle thicker than the appropriate ventricle. The wall surfaces of the left ventricle that the heart are thicker 보다 the best ventricle since the left ventricle pumps the blood transparent the body and also also against the greater pressure in compassion to the ideal ventricle. Endocardium: This is the innermost layer the lines the inner wall surface of the love and additionally lines the heart valves. The endocardium is further subdivided into two layers: (1) an within endothelial cell layer the lines the heart chamber and (2) the 2nd layer is the subendocardial layer i m sorry is a connective organization layer in continuation with the connective tissue of the myocardial connective organization layer. The impulse-conduction system the the love is inserted in this subendocardial layer.
The heart of the vertebrates is a muscular body organ that pumps blood to various parts that the body. It moves the blood v rhythmic contractions. The wall surface of the heart is made up of 3 layers: (1) epicardium (outermost), (2) myocardium (middle), and also (3) endocardium (innermost).
figure 2: Myocardium and also endocardium. Source: Alessandro Scalese and also Mikael Häggström, M.D., CC-BY-SA 4.0.

Cardiac Muscle Histology

What is cardiac muscle? it is crucial to know the an interpretation of cardiac muscles. Basically, cardiac muscles space the involuntary, striated muscles the are made up of cardiac muscle cells or cardiomyocytes.

Cardiac muscles are one of the three varieties of vertebrate muscle (the other two being, skeletal muscles and smooth muscles).Cardiac muscles share few of the functions of both smooth muscles and skeletal muscles. Prefer skeletal muscles, cardiac muscles space striated and also can induce solid contractions too can initiate continuous contractions prefer smooth muscles. However, cardiac muscle possess details unique characteristics.

The cardiomyocytes room arranged in a helical or overlapping spiral pattern and are fastened to the fibrous skeleton that the heart. This helical pattern outcomes in a facility 3-dimensional framework network.

Cardiac muscle fibers space elongated cylindrical in shape, around 50–100 μm long and 10–25 μm wide. These muscle fibers are made up of distinct quadrangular cells having a centrally situated clear oval nucleus. The rectangular-shaped muscle cell are often branched and joined end to end forming a syncytium.

The 2 cardiac muscle cells satisfy to kind a unique junctional complicated known together an intercalated disc. This intercalated disks contain three vital components:

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Figure 3: Cardiac muscle structure. (a) Cardiac muscle cells. (b) Cardiac muscle cells mirroring the nuclei and intercalated discs. (c) Desmosomes and also gap junctions. Source: OpenStax.org

Structurally, intercalated disk to represent the twin membranes formed because of tightly bound cell by desmosomes that are linked by void junctions. This is required for delivering cell-to-cell electric impulse conduction. Gap junctions assist in the electric coupling that the muscle cells, thereby promoting the synchronized beating of the heart muscles.

Cardiac muscle cell are qualified of strong, continuous, and also rhythmic contractions produced automatically. Though, the autonomic concerned system and hormones can change the contractility of the love muscle cells.

Under a microscope, intercalated disks can be seen as faint lines to run perpendicular to the long axis the the cardiac muscle fiber. In the adult human, a brown shade pigment located at a perinuclear position deserve to be generally seen. This brown color pigment is “lipofuscin“, which is thought about as “wear and tear” pigment, is the build-up of the lipids, phospholipids, and also proteins ~ lipid peroxidation.

Sarcomeres are the useful unit of the cardiac myocyte and also contraction. Within every myocyte, the contractile fibers of the sarcomeres space surrounded through transverse discs, known as Z-bands. Every myocyte possesses a number of sarcomeres that room stacked end to end and also circumferentially creating a “cable effect” within the cell.

There space two necessary proteins uncovered in cardiac muscle cells are myosin and also actin. The special filaments are comprised of myosin while slim filaments are of actin. These two proteins collectively type the myofibrillar filament that features to carry out the contractile role in the cardiac muscle tissues.

The sarcoplasm (i.e., the cytoplasm that the cardiac myocytes) the the cardiac muscle cells is very rich in mitochondria as result of the high energy requirement for consistent contractions. Oxidative phosphorylation wake up in the cardiac myocytes to accomplish the power requirements. Thus, these muscles need an uninterrupted it is provided of oxygen. The blood is provided to the myocardium by coronary arteries. Additionally, glycogen granules are existing in the myofibrils to support the extr energy requirement.

The myocardium has the biggest oxygen requirement and also is most critically influenced by the reduction in blood flow. Reduction in blood flow i.e. ischemiacan it is in potentially an important for this muscles. Also, cardiac muscles room resistant come fatigue. Essentially, cardiac muscles develop their own action potential, i.e. Myogenic in nature; however, details modified muscle cells are dedicated to create the stimulus because that the heartbeat and also conduct the impulse to different segments that the myocardium system.

These committed cells kind the myocardial conduction system that is composed of the sinoatrial node, atrioventricular node, the bundle the His, and also Purkinje fibers. 99% that the myocardium is made up of contractile cells while 1% the the cell are component of the myocardial conducting system.

The conducting myocardial cells are dedicated muscle cell that function in the same method as neurons. These conducting cell initiate and also spread the action potential throughout the love while the contracting myocardial cells take up this activity potential come pump the love rhythmically and also regularly.

Functions the the Myocardium

To know the circulatory system, it is important to know what is the role of the myocardium. The primary duty of the cardiac muscle is to wake up contractions and relaxation in the heart. The contraction action results in the pump of the blood native the ventricles to the entirety body if the relaxation activity of the cardiac muscles permits the atrium to receive blood. This beating that the love pumps the blood transparent the body ensuring that each cell and also tissue the the body receives the blood supply.

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Cardiac muscles are essentially under the control of an autonomous concerned system that releases the time nervous impulses signaling the love cells come contract and also relax in a rhythmic pattern.