liver

from Wikipedia, the free encyclopedia

The liver ( Latin iecur , ancient Greek ἧπαρ Hepar ) is the central organ of metabolism and the largest gland in the body in vertebrates . The most important tasks are the production of vital proteins (e.g. coagulation factors ), the utilization of food components (e.g. storage of glycogen and vitamins ), the production of bile and the associated breakdown and excretion of metabolic products, drugs and toxins (see also enterohepatic cycle ). Nutrients that are absorbed from the intestine into the blood reach the liver via the portal vein ( vena portae ) and are then released into or removed from the blood as required. It consists of left and right halves of the liver.

Location of the liver (2) in the human body

In humans , the liver is located in the right upper abdomen directly below the diaphragm and the left parts protrude into the left half of the upper abdomen.

etymology

The old Germanic name ( Middle High German leber [e] , Old High German lebara ) cannot be interpreted with certainty. The designation can be a substantiated adjective to (stick) and would then actually mean "the sticky, the oily, the fat". On the other hand, the word can be a form of verb live to be because the liver until the 17th century as blood -forming organs and how the heart as the "seat of life" was. Probably with Latin iecur related ancient Greek hepar (to Sanskrit yákṛt or Avestan yākarɚ ) goes on a Indo-European root * IEQ U r back.

Liver structure

The division of the liver into lobes

Liver of a human (border between the halves marked in green)
Liver of a sheep, intestines with the gallbladder

The human liver weighs around 1500 to 2000 g and is a soft, evenly structured organ , most of which is located in the right upper abdomen . It can be divided into two large lobes of the liver. The right lobe of the liver ( lobus dexter ) lies under the diaphragm and is partially fused with it. It is larger than the left lobe of the liver ( lobus sinister ), which extends into the left upper abdomen. There are also two other, smaller lobes: the square lobe ( lobus quadratus ) and the "tailed" lobe ( lobe caudate ).

care

On the underside of the liver is what is known as the porta hepatis , through which the portal vein and the hepatic arteries enter the liver and through which the bile duct leaves them. The hepatic artery ( Arteria hepatica propria ) transports the oxygen-rich blood from the heart, the portal vein carries blood with food components from the stomach and intestines, with breakdown products of the spleen and with hormones from the pancreas to the liver. About 25% of the liver is supplied with oxygen-rich blood from the hepatic artery and about 75% with blood from the portal vein. The lymph drainage occurs through the liver lymph nodes .

Functional division of the human liver

Liver segments in axial slices

According to Claude Couinaud (1922–2008), the human liver is divided into eight segments. This traditional subdivision has been questioned in more recent studies, which - individually varying - found 9 to 44 secondary branches of the portal vein. An anecdote claims that Couinaud used the Paris arrondissements as a guide when numbering the segments . He himself relegated this claim to the realm of modern sagas . Despite the relative inaccuracy of the traditional segmentation, it is still used as a standard for anatomical and surgical orientation.

Since the human liver - in contrast to that of many animals - shows only a few fissures, the division into two by the ligamentum falciforme hepatis (see liver ligaments ) is very noticeable. It led to the older anatomical division into a left and right lobe. The functional and actual limit (the Rex-Cantlie line) extends perpendicularly from the gall bladder to the lower vena cava, and the liver is divided into two liver halves (Hemihēpata). The splitting of the portal vein divides the liver horizontally into an upper (cranial) and a lower (caudal) segment group.

  • Left half of the liver:
    • Segment 1 - caudate lobe
    • Segment 2 - cranial part of the lateral segment
    • Segment 3 - caudal part of the lateral segment
    • Segment 4 - quadratus lobe
      • Segment 4a - cranial part
      • Segment 4b - caudal part
  • Right half of the liver:
    • Segment 5 - the caudal part of the segmentum anterius
    • Segment 6 - caudal part of the segmentum posterius
    • Segment 7 - cranial part of the segmentum posterius
    • Segment 8 - cranial part of the segmentum anterius

In 2000, the publication and worldwide implementation of a redefinition of the anatomical liver divisions by an expert group of the International Hepato-pancreato-biliary Association, which was called Brisbane terminology . New to this terminology, which has been in common use since then, is:

  • The use of Arabic numbers instead of Roman numbers for segment assignment .
  • The introduction of the term sector , which defines a functional unit of two segments lying on top of one another.

Liver ligaments

The liver is attached to the abdominal cavity by several ligaments . These ligaments do not represent connective tissue structures, but double folds (duplicates) of the peritoneum :

The posterior ( dorsal ) edge of the liver is connected to the diaphragm via the coronary ligament . The coronary ligament merges into the triangular ligamentum triangulare dextrum or sinistrum on both sides , which encircle the so-called bare surface of the liver (area nuda) with direct contact to the diaphragm without an intervening peritoneum. On the side of the diaphragm pulls the ligament coronarium the falciform ligament of the liver ( "Crescent liver Band") perpendicular to the side of the abdomen ( ventral ). The ligamentum falciforme hepatis originally extends as far as the navel , because in the fetus it represents the mesentery of the umbilical vein. The umbilical vein itself closes immediately after birth and is retained as a rounded, connective tissue strand, which is known as the ligamentum teres hepatis through the free edge of the ligamentum falciform hepatis pulls and reaches the venae hepaticae or the portal vein as ligamentum venosum hepatis .

On the abdominal cavity side, the liver is connected to the stomach and the duodenum via the small network ( omentum minus ). The appendix fibrosa also fixes the left lobe of the liver to the diaphragm.

Fine structure of the liver

Glisson's triad of the human liver
Glisson triad of rat liver, 1  interlobular artery, 2 interlobular veins , 3 biliferous ducts (Masson-Goldner stain)
Schematic representation of a central venous lobe of the liver . The Glisson triad is located between the hexagons , picture below right. They consist of: interlobular ductus biliferi (green), interlobular artery (red) and interlobular vein (purple)
Enlargement of the schematic representation of a central venous lobe of the liver .

The liver lobes are further subdivided into tiny liver lobes (max. 1–2 mm). These are hexagonal structures in the section, which mainly consist of liver cells ( hepatocytes ). The hepatocytes usually have several cell nuclei and are arranged in strands ("liver cell bars"). The portal fields are located at the corner points of neighboring liver lobes . An arteria interlobularis (a branch of the hepatic artery ), a vena interlobularis (a branch of the portal vein) and a bile duct ( ductus biliferus ) run in each of these fields . These vessels are known as the Glisson triad ( Glisson's triangle ). The Glisson's triad can be seen less clearly in humans under the microscope than in some animals, e.g. B. Pig, rat (see fig.).

The enlarged capillaries of the liver ( liver sinusoids ) are located between the liver cells . These sinusoids are lined by a discontinuous endothelium (basal lamina is missing) and contain special macrophages , the Kupffer cells (old name Kupffer star cell ). The sinusoids transport the blood of the portal vein together with the blood from the hepatic artery through the liver lobules in the direction of the lobule centers, where it is taken up by a central vein ( vena centralis ). The central veins unite to form larger veins ( venae sublobulares ) and finally flow into the mostly three hepatic veins ( venae hepaticae ).

The space between the endothelial cells of the liver sinusoids and the liver cells is called the Disse space (after Josef Disse), in which the actual exchange of substances between blood and hepatocytes takes place. In the Disse space there is blood plasma, as well as the so-called Ito cells , which contain vitamin A and are used for fat storage. They are also considered to be the producers of intralobular connective tissue fibers and acquire pathophysiological importance in the context of liver cirrhosis .

The bile capillaries are only depressions of the liver cells within the lobules of the liver; only after exiting the lobules do they get their own wall and become the bile ducts with a single-layer prismatic epithelium . The bile flows from the small bile ducts of a portal field via larger bile ducts from the liver.

In addition to the division of the liver into the classic central vein lobules (lobules) described above, the division into liver acini (singular: liver acini) is helpful. This is more a functional than a histological approach. The middle axis of an acinar represents a bundle with the terminal branches of the supply, i.e. the vessels of the Glisson triad, which run along the edge of the classic lobule. The advantage of this classification is that it takes into account that one supply bundle can discharge the blood into both adjacent lobules.

The hepatocytes closest to the bundle of supplies are best supplied with oxygen and nutrients, which is why this area is referred to as zone 1 of the acinar. Zones 2 and 3 are further to the center of the classic lobule.

Benefits of the liver

The liver is closely involved in the control of the glucose , fat and protein metabolism . Glucose is absorbed by the intestinal blood and passed on to the rest of the body in a controlled manner. Any excess is stored as glycogen . When there is a need for energy, the storage material is converted into glucose . The liver - controlled by hormones such as insulin and glucagon - influences the blood sugar level and can keep it constant regardless of the food intake. In the liver, insulin converts sugar into the storage form glycogen and inhibits the breakdown of fat. The hormone glucagon in turn stimulates the liver to break down glycogen and thus acts as an antagonist to insulin.

Compared to other organs in the body, the liver has a relatively strong ability to regenerate. If a part dies, if the liver is injured or otherwise damaged, the affected tissue can be regenerated. The prerequisite for a new formation is that the cause of the injury has been removed, less than fifty percent of the functional mass of the organ has been damaged, and the liver has been able to maintain its ability to regenerate during the injury. This property is often exploited in liver transplants . There is no scarring, for example in the case of skin injuries .

The ability of the liver to regenerate is already reflected in Greek mythology: In the legend of Prometheus , the liver is forged on a rock as a punishment for handing over fire to people. Every day an eagle chops out a part of its liver that will grow back until the next day.

Liver enzymes

In the case of liver disease, blood tests for liver enzymes provide information on the type and extent of the disease ( liver values ). As everywhere in the body, enzymes are also required in the liver to maintain the liver's metabolic performance. Normally these proteins are part of the cytoplasm of the liver cells (hepatocytes). However, these enzymes are also produced by other tissues and cannot be assigned to the liver without exception. If the liver cells are damaged, these enzymes are increased in the blood serum. Depending on which enzymes are elevated, one can often infer the type of disease. The level of the increase in enzyme in the serum corresponds to the extent to which the liver cells are damaged. Since these enzymes only get into the blood when liver cells are destroyed, a concentration that is too high is an indicator of liver disease. The liver values ​​can be checked in a small blood count. Cell damage can be caused by viral infections, alcohol, poisoning or tumors. All of the enzymes in liver cells are also found in other cells in the body, such as the heart and skeletal muscles. However, some enzymes are only increased in the serum (liquid component of blood without fibrinogen) when liver cells are damaged.

Liver enzymes are often measured

  • GOT = AST = ASAT = glutamate oxaloacetate transaminase / aspartate aminotransferase : Increased in the case of poisoning by alcohol or other toxic substances, in the case of inflammation and liver congestion, especially in acute liver diseases.
  • GPT = ALT = ALAT = glutamate pyruvate transaminase / alanine aminotransferase : the quotient AST / ALT is analyzed. A value between 0.8 and 1.0 indicates slight liver damage; if the value is above 1.0, this is an indicator of severe liver damage. Possible causes are a tumor, inflammation, or poisoning of the liver.
  • Gamma-GT = γ-GT = GGT = gamma-glutamyl-transferase  : An increase in this value in the blood count is the result of poisoning or biliary congestion in the liver.
  • AP = alkaline phosphatase : If an increased value is measured in the blood count, this can be an indication of liver carcinoma, liver cirrhosis, hepatitis or biliary congestion.

The gamma GT is the most sensitive parameter for damage to the liver cells and the bile duct system.

Damage and diseases (hepatopathies)

Idioms

Since the liver was previously seen as the seat of emotions and temperaments as well as the originator of blood and instincts, it became the subject of several idioms. The liver, from which the “bile” originates, is still considered the seat of anger today . Examples of corresponding idioms:

  • “A louse runs (creeps) over my liver” means I'm angry or I'm in a bad mood.
  • “To talk freely from the liver ” means to speak openly or to say what you mean and think without inhibitions, or to not impose any pressure on yourself .
  • “ To play the offended liver sausage ” means to be offended or offended for no good reason .
  • “Having a dry liver” means enjoying drinking (alcohol).

See also

literature

  • Wolfgang F. Caspary et al. a. (Ed.): Therapy of liver and gall bladder diseases. Springer-Verlag , Berlin 2000, ISBN 3-540-67390-3 .
  • Helmut Denk u. a .: Pathology of the liver and biliary tract. (= Special Pathological Anatomy. Volume 10). Springer-Verlag, Berlin 2000, ISBN 3-540-65511-5 .
  • Hansludwig Hagen: The physiological and psychological importance of the liver in antiquity , Rheinische Friedrich-Wilhelms-Universität Bonn , 1961.
  • Erwin Kuntz , Hans-Dieter Kuntz: Practical Hepatology. History, morphology, biochemistry, diagnostics, clinic, therapy. Barth , Heidelberg 1998, ISBN 3-335-00568-6 .
  • Ellen Schmidt et al. a. (Ed.): Liver Diseases. Pathophysiology, diagnostics, therapy. Wissenschaftliche Verlagsgesellschaft , Stuttgart 2000, ISBN 3-8047-1640-7 .
  • Hans Adolf Kühn: diseases of the liver. In: Ludwig Heilmeyer (ed.): Textbook of internal medicine. Springer-Verlag, Berlin / Göttingen / Heidelberg 1955; 2nd edition, ibid. 1961, pp. 847-875.
  • Renate Lüllmann-Rauch: pocket textbook histology. Georg Thieme Verlag , Stuttgart 2006.
  • Nikolaus Mani : The historical basis of liver research; I: The concepts of anatomy, physiology and pathology of the liver in antiquity; II: The History of Liver Research from Galen to Claude Bernard. Basel and Stuttgart 1959 and 1967 (= Basel publications on the history of medicine and biology , 9 and 21).

Web links

Commons : Liver  album with pictures, videos and audio files
Wikibooks: Liver  - learning and teaching materials
Wikiquote: Liver  Quotes
Wiktionary: Liver  - explanations of meanings, word origins, synonyms, translations
Wiktionary: hepatic  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ^ The dictionary of origin (=  Der Duden in twelve volumes . Volume 7 ). 2nd Edition. Dudenverlag , Mannheim 1989, p. 409 . See also DWDS ( "Leber" ) and Friedrich Kluge : Etymological dictionary of the German language . 7th edition. Trübner, Strasbourg 1910 ( p. 281 ).
  2. ↑ Alois Walde : Latin etymological dictionary. 3rd edition, obtained from Johann Baptist Hofmann , 3 volumes. Heidelberg 1938-1965, Volume 1, p. 673.
  3. ^ Johann Baptist Hofmann : Etymological dictionary of the Greek. R. Oldenbourg Verlag , Munich 1950, p. 108 f.
  4. ^ C. Couinaud: Le Foie. Etudes anatomiques et chirurgicales. Masson & Cie, Paris 1957.
  5. ^ JH Fasel: Portal venous territories within the human liver: an anatomical reappraisal. In: Anat Rec . 291 (6), 2008 Jun, pp. 636-642. PMID 18484609
  6. ↑ Jean-Nicolas Vauthey, Giuseppe Zimmitti, Junichi Shindoh: From Couinaud to molecular biology: the seven virtues of hepato-pancreato-biliary surgery . In: HPB . tape 14 , no. 8 , p. 493-499 , doi : 10.1111 / j.1477-2574.2012.00502.x , PMID 22762396 , PMC 3406345 (free full text) - ( elsevier.com ).
  7. ^ Keith L. Moore, Arthur F. Dalley: Clinically oriented Anatomy. 5th edition. Lippincott Williams & Wilkins, 2006, ISBN 0-7817-3639-0 , p. 293.
  8. ^ SM Strasberg et al .: The Brisbane 2000 Terminology of Liver Anatomy and Resections. HPB 2, pp. 333-339. doi: 10.1016 / s1365-182x (17) 30755-4
  9. ^ Hans Frick, Helmut Leonhardt , Dietrich Starck : Special anatomy. Volume 2, Georg Thieme Verlag , Stuttgart 1992, ISBN 3-13-356904-X , p. 132.
  10. ↑ R. Lüllmann-Rauch: Histology. 2003, p. 340.
  11. ↑ Schematic representation and differences between central vein lobules (lobules) and liver acini
  12. ↑ Renate Lüllmann-Rauch: Histology. Understand - Learn - Look Up . Georg Thieme Verlag , Stuttgart.
  13. ↑ What are liver values, when do they become dangerous and how are they treated? Retrieved March 22, 2019 . [They instead of them in the original.]
  14. ^ Meyers Kleines Lexikon , 9th edition, Volume 2, Bibliographisches Institut , Leipzig 1933, p. 1359.
  15. ↑ Günter Thiele (Ed.): Handlexikon der Medizin , Urban & Schwarzenberg , Volume 4 (L – Z); Munich, Vienna, Baltimore without year, p. 2194.
  16. ^ Linus Geisler : "Krankenpflege", internal medicine , Volume II, Verlag Wilhelm Kohlhammer , 10th edition, Stuttgart, Berlin, Cologne, Mainz 1970, ISBN 3-17-007038-X , p. 34.
  17. ↑ Willibald Pschyrembel: Clinical Dictionary , 267th edition, de Gruyter , Berlin, Boston 2017, ISBN 978-3-11-049497-6 , pp. 1030 and 1712.
  18. ↑ Günter Thiele (Ed.): Handlexikon der Medizin , Urban & Schwarzenberg , Munich, Vienna, Baltimore no year, Volume 4 (S – Z), p. 2322.
  19. ^ Meyers Kleines Lexikon , 9th edition, Volume 2, Bibliographisches Institut , Leipzig 1933, p. 1359.
  20. ^ Ludwig August Kraus: Kritisch-etymologisches medicinisches Lexikon , 3rd edition, Verlag der Deuerlich- und Dieterichschen Buchhandlung, Göttingen 1844, p. 458 (Hepathyderos).
  21. ↑ Ludwig August Kraus: Kritisch-etymologisches medicinisches Lexikon , 3rd edition, Verlag der Deuerlich- und Dieterichschen Buchhandlung, Göttingen 1844, p. 457.
  22. ↑ Jerry Stannard: Medieval hepatic therapy and some folk medical survivals. In: Würzburg medical history reports. Volume 6, 1988, pp. 207-223.
  23. ↑ Der Duden in twelve volumes , Dudenverlag , Volume 11: Redewendung , Mannheim 1992, p. 443.
  24. ↑ Der Sprach-Brockhaus , Eberhard Brockhaus Verlag, Wiesbaden 1949, p. 365.
  25. ↑ Der Sprach-Brockhaus , Eberhard Brockhaus Verlag, Wiesbaden 1949, p. 365.
  26. ^ German dictionary , school education work, Verlag Hans Witte, 3rd edition, Freiburg im Breisgau 1965, p. 520.
  27. ^ German dictionary , school education work, Verlag Hans Witte, 3rd edition, Freiburg im Breisgau 1965, p. 520.
  28. ↑ Der Sprach-Brockhaus , Eberhard Brockhaus Verlag, Wiesbaden 1949, p. 365.
  29. ^ German dictionary , school education work, Verlag Hans Witte, 3rd edition, Freiburg im Breisgau 1965, p. 520.
  30. ↑ Der Sprach-Brockhaus , Eberhard Brockhaus Verlag, Wiesbaden 1949, p. 365.
  31. ^ German dictionary , school education work, Verlag Hans Witte, 3rd edition, Freiburg im Breisgau 1965, p. 520.