Myocardium 502364 224196790 2008-07-07T19:31:15Z WriterHound 266293 added pic {{Merge|cardiac muscle|date=June 2008}} {{Unreferenced|date=January 2008}} {{Infobox Anatomy | Name = Myocardium | Latin = | GraySubject = | GrayPage = | Image = Heart myocardium diagram.jpg| Caption = | Image2 = | Caption2 = | Precursor = | System = | Artery = [[coronary artery|coronary arteries]] | Vein = | Nerve = | Lymph = | MeshName = | MeshNumber = | DorlandsPre = m_24 | DorlandsSuf = 12554874 | }} '''Myocardium''' is the [[muscle|muscular]] tissue of the [[heart]]. ==Relationship to other layers== The other tissues of the heart are: * the [[endocardium]] (inner lining, effectively a specialized [[endothelium]]) * the [[epicardium]] (a [[connective tissue]] layer around the heart with a serous surface. It may be considered as the inner (visceral) layer of the [[pericardium]]) ==Composition== The myocardium is composed of specialized [[cardiac muscle]] cells with an ability not possessed by muscle tissue elsewhere in the body. Cardiac muscle, like other muscles, can [[muscle contraction|contract]], but it can also carry an [[action potential]] (i.e. [[electrical conduction|conduct electricity]]), like the [[neurons]] that constitute [[nerve]]s. Furthermore, some of the cells have the ability to generate an action potential, known as [[cardiac muscle automaticity]]. The blood supply of the myocardium is carried by the [[coronary artery|coronary arteries]]. The myocardium is subject to two opposed electrical subsets of control. First order electrical control of the myocardium is derived from the sinoatrial node. Propagation of first order control from the sinoatrial node is closely tied to sympathetic discharge. Second order electrical control of the myocardium is closely tied to parasympathetic influence from the spinal vertebral ganglia and vagus nerves. ==Pathology== Occlusion of the coronary arteries by [[atherosclerosis]] and/or [[thrombosis]] can lead to [[myocardial infarction]]. Certain viruses lead to [[inflammation]] of the myocardium, or [[myocarditis]]. [[Cardiomyopathies]] are inherent diseases of the myocardium, many of which are caused by genetic mutations. Failure of the heart to contract properly (for various reasons) is often termed [[heart failure]] although the proper term for this condition is myocardial failure. [[Heart failure]] is a general term referring to overwhelming heart disease from many causes (e.g., myocardial failure, valvular heart disease, increased ventricular stiffness) resulting in the inability of the heart to maintain normal ventricular filling pressure (resulting in [[fluid retention]], [[edema]], [[pulmonary oedema]], [[hepatomegaly]]) and/or reduced blood flow to the body either at rest or during exercise. Myocardial failure resulting in heart failure results in a shortened [[life expectancy]] and decreased [[quality of life]]. ==Disease of myocardium== [[Noncompaction Cardiomyopathy]], is when the Myocardium tissue fails to compact as the human embryo develops. Disease of the myocardium can also be considered to be ischemic (poor blood supply to the heart muscle) or nonischemic, implying disease within the heart muscle itself. 1. Ischemic myocardial disease is well described and is amenable to vessel bypass, [[stents]], applied [[growth factors]] and many other interventions. a. [[Diabetes]] is perhaps the best known physiologic model for accelerated ischemic disease of the myocardium. 2. Nonischemic myocardial disease (see also nonischemic cardiomyopathy) is an entirely different entity in myocardial disease. a. Chagasic heart failure (see also [[Carlos Chagas]]) is perhaps the best known physiologic model in myocardial autonomic insufficiency. ==See also== *[[Cardiac muscle]] ==External links== * {{BUHistology|03802ooa}} *[http://www.antibodypatterns.com/cardiacmuscle.php Immunocytochemical image of cardiac muscle] *[http://www.ii.bham.ac.uk/clinicalimmunology/CISimagelibrary/myocardial_Ab.htm Myocardial antibody] {{Heart}} {{Muscle tissue}} [[Category:Cardiac anatomy]] [[de:Herzmuskel]] [[el:Μυοκάρδιο]] [[es:Miocardio]] [[eu:Miokardio]] [[fr:Myocarde]] [[it:Miocardio]] [[la:Myocardium]] [[nl:Hartspierweefsel]] [[ja:心筋]] [[nn:Myokard]] [[pt:Miocárdio]] [[ru:Миокард]] [[simple:Myocardium]] [[fi:Myokardium]] [[uk:Міокард]]