Endocardium

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The endocardium or the inner lining of the heart ( inner heart coating) is the innermost layer of the heart wall . The endocardium also includes the four heart valves .

anatomy

The endocardium is the innermost of the three layers of the heart wall. It consists of endothelium and connective tissue , is approx. 0.5–1.0 mm thick and can even be histologically divided into the following layers from inside to outside:

  • The endothelium is formed by a continuous, single-layer squamous epithelium .
  • The subendothelial stratum consists of loose connective tissue with sparse elastic fibers .
  • The stratum myoelasticum can be further subdivided into the lamina elastica interna , the lamina muscularis and the lamina fibroelastica externa . This layer consists of smooth muscle and abundant collagen fibers. Blood vessels and nerve fibers are also found here and there . Smooth muscles are mainly developed in the area of ​​the atria, while they are largely absent in the area of ​​the ventricles.
  • The Tela subendocardialis is a loose layer of connective tissue that also contains Purkinje fibers .

The endocardium covers the entire inner surface of the heart - including the papillary muscles and tendon threads (however, the tela subendocardialis is missing here ) - and forms the four heart valves : mitral valve , tricuspid valve , aortic valve and pulmonary valve . The valves have a stiffened network of collagen connective tissue fibers, the "valve structure". The endocardium has hardly any blood vessels (bradytropic tissue), and nutrition comes from the blood in the interior of the heart.

function

With its smooth surface, the endocardium prevents the blood from sticking to the heart wall and forming clots. In addition, the smooth surface makes the blood flow more even and the heart work more efficiently. Even small bumps, e.g. B. after inflammation ( endocarditis ), disrupt the regular blood flow and can lead to a reduction in cardiac output. The smooth muscles in the area of ​​the atria presumably serve to adjust the wall tension.

The heart valves act like mechanical valves and force blood flow in one direction. For example, the mitral valve, which is closed during systole , prevents blood from flowing back from the left ventricle into the left atrium when the heart muscle contracts.

Diagnosis

Since there is a large difference in impedance between connective tissue and blood , the endocardium, including the heart valves, can be shown very well using echocardiography . The endocardium is shown as a very thin, light layer. Using transesophageal echocardiography , the detailed recognition of the echocardiography can be increased again; the sensitivity of the detection of vegetation for the diagnosis of cardiac inflammation ( endocarditis ) increases with this technique to about 90%. The formation of thrombi in Löffler endocarditis can also be demonstrated sonographically.

If bacterial endocarditis is suspected, blood tests are very important, such as the determination of inflammation values ​​( leukocyte count , concentration of CRPs ), repeated blood cultures , detection of bacterial DNA.

Diseases

Inflammatory changes in the area of ​​the endocardium are called endocarditis . In veterinary medicine , the primarily degenerative changes in the inner lining of the heart that often occur in animals are referred to as endocardiosis (heart valve fibrosis ), which can also occur as a consequence of endocarditis.

In humans , bacterial endocarditis is mostly triggered by streptococci or other bacteria that are washed in by other infections that have not healed . The main complication here is involvement of the heart valves, which can lead to a massive reduction in cardiac output. In particular, an inadequate function (insufficiency) of all four heart valves can cause heart failure , the severity of which increases as the valve function is restricted.

Other diseases of the endocardium and the valves:

Individual evidence

  1. ↑ Renate Lüllmann-Rauch: Pocket textbook histology. 3rd, completely revised edition. Thieme, Stuttgart et al. 2009, ISBN 978-3-13-129243-8 , p. 258.
  2. ↑ a b c Johannes W. Rohen, Elke Lütjen-Drecoll: Functional Histology: Brief textbook on cytology, histology and microscopic human anatomy according to functional aspects . Schattauer, Stuttgart 2000, ISBN 3-7945-2044-0 , p. 159 .
  3. ^ Claus-Henning Bley et al.: I care anatomy, physiology . Georg Thieme, Stuttgart 2015, ISBN 978-3-13-165621-6 , p. 113 .
  4. ^ Robert F. Schmidt, Florian Lang, Manfred Heckmann: Physiology of humans: with pathophysiology . 29th edition. Springer, Berlin 2007, ISBN 978-3-540-26416-3 , pp. 578 .
  5. ↑ Hans Christian Lederhuber: Basics Cardiology . Elsevier, Urban & Fischer, 2005, ISBN 3-437-42186-7 , pp. 20 .
  6. ↑ a b c d e Rainer Hoffmann, Peter Hanrath: Diseases of the endocardium . In: Wolfgang Gerok (Hrsg.): The internal medicine: reference work for the specialist . Schattauer, Stuttgart 2007, ISBN 978-3-7945-2222-4 , pp. 216-225 .
  7. ^ Gebhard Mathis: Picture Atlas of Lung and Pleural Sonography . 4th edition. Springer Science & Business Media, Berlin 2006, ISBN 3-540-34106-4 , pp. 235 .
  8. ↑ Wolfgang Baumgärtner, Achim Dieter Gruber: Special pathology for veterinary medicine . Enke, Stuttgart 2015, ISBN 978-3-8304-1174-1 .

See also