Endocardium 604057 220977904 2008-06-22T14:13:21Z VolkovBot 3035831 robot Adding: [[bs:Endokard]] {{Infobox Anatomy | Name = {{PAGENAME}} | Latin = | GraySubject = | GrayPage = | Image = | Caption = | Image2 = | Caption2 = | Precursor = | System = | Artery = | Vein = | Nerve = | Lymph = | MeshName = | MeshNumber = | DorlandsPre = e_08 | DorlandsSuf = 12331748 | }} The '''endocardium''' is the innermost layer of tissue that lines the chambers of the heart. Its [[Cell (biology)|cells]], [[embryology|embryologically]] and [[biology|biologically]], are similar to the [[endothelium|endothelial]] cells that line [[blood vessel]]s. The ''endocardium'' overlies the much more voluminous [[myocardium]], the muscular tissue responsible for the contraction of the heart. The outer layer of the heart is termed [[epicardium]] and the heart is surrounded by a small amount of fluid enclosed by a fibrous sac called the [[pericardium]]. ==Function== Recently, it has become evident that the endocardium, which is primarily made up of endothelial cells, controls myocardial function. This modulating role is separate from the homeometric and heterometric regulatory mechanisms that control myocardial contractility. Moreover, the endothelium of the myocardial (heart muscle) capillaries, which is also closely appositioned to the cardiomyocytes (heart muscle cells) are involved in this modulatory role. Thus, the cardiac endothelium (both the endocardial endothelium and the endothelium of the myocardial capillaries) controls the development of the heart in the embryo as well as in the adult, for example during hypertrophy. Additionally, the contractility and electrophysiological environment of the cardiomyocyte are regulated by the cardiac endothelium. The endocardial endothelium may also act as a kind of blood-heart barrier (analogous to the blood-brain barrier), thus controlling the ionic composition of the extracellular fluid in which the cardiomyocytes bathe. == Role in disease == In [[myocardial infarction]], [[ischemia]] of the [[myocardium]] can extend to the endocardium, disrupting the inner lining of the heart ("Transmural" [[infarction]]). Less extensive [[infarction]]s are often "subendocardial" and do not affect the endocardium. Subendocardial [[infarction]]'s are much more dangerous than Transmural [[infarction]]s because they create an area of dead tissue surrounded by a boundary region of damaged [[myocyte]]s. This damaged region will conduct impulses more slowly, resulting in irregular rhythms. The damaged region may enlarge or extend and become more life-threatening. During Depolarization the impulse is carried from endocardium to epicardium, and during Repolarization the impules moves from epicardium to endocardium. In [[endocarditis|infective endocarditis]], the ''endocardium'' (especially the endocardium lining the [[heart valve]]s) is affected by [[bacterium|bacteria]]. ==External links== * {{UIUCHistologySubject|644}} * {{OklahomaHistology|64_06}} - "Heart and AV valve" (atrial endocardium) * {{OklahomaHistology|64_07}} - "Heart and AV valve" (ventricular endocardium) {{Heart}} [[Category:Cardiac anatomy]] [[bs:Endokard]] [[de:Endokard]] [[es:Endocardio]] [[fr:Endocarde]] [[it:Endocardio]] [[la:Endocardium]] [[nl:Endocard]] [[pt:Endocárdio]] [[sk:Endokard]] [[fi:Endokardium]]