THE LIVER 



1193 





ligament. The left triangular ligament (ligamentum triangulare sinistrum) is a fold 

 of some considerable size, which connects the posterior part of the upper surface 

 of the left lobe to the diaphragm; its anterior layer is continuous with the left 

 layer of the falciform ligament. 



The round ligament (ligamentum teres hepatis) is a fibrous cord resulting from the 

 obliteration of the umbilical vein. It ascends from the umbilicus, in the free margin 

 of the falciform ligament, to the umbilical notch of the liver, from which it may be 

 traced in its proper fossa on the inferior surface of the liver to the porta, where 

 it becomes continuous with the ligamentum venosum. 



Fixation of the Liver. Several factors contribute to maintain the liver in 

 place. The attachments of the liver to the diaphragm by the coronary and tri- 

 angular ligaments and the intervening connective tissue of the uncovered area, 

 together with the intimate connection of the inferior vena cava by the connective 

 tissue and hepatic veins would hold up the posterior part of the liver. Some sup- 

 port is derived from the pressure of the abdominal viscera which completely fill 

 the abdomen whose muscular walls are always in a state of tonic contraction. The 

 superior surface of the liver is perfectly fitted to the under surface of the diaphragm 

 so that atmospheric pressure alone would be enough to hold it against the dia- 

 phragm. The latter in turn is held up by the negative pressure in the thorax. The 

 lax falciform ligament certainly gives no support though it probably limits lateral 

 displacement. 



Pericardial cavity 



Anterior watt of 

 pericardium 



Lower wall of 

 pericardium 



Vilelline duct 



Liver 

 Bile duct 



Truncus arteriosus 



Dorsal mesocardium 



Atrium 



Cuvierian duct 



Umbilical vein 

 Vitelline vein 



Communication 

 between pericardial 

 and peritoneal cavities 



Peritoneal cavity 



Fia. 1088. Liver with the septum transversum. Human embryo 3 mm. long. (After model and figure by His.) 



Development. The liver arises in the form of a diverticulum or hollow outgrowth 

 from the ventral surface of that portion of the gut which afterward becomes 

 the descending part of the duodenum (Fig. 1088). This diverticulum is lined by 

 entoderm, and grows upward and forward into the septum transversum, a mass 

 of mesoderm between the vitelline duct and the pericardial cavity, and there gives 

 off two solid buds of cells which represent the right and the left lobes of the liver. 

 The solid buds of cells grow into columns or cylinders, termed the hepatic cylinders, 

 which branch and anastomose to form a close meshwork. This network invades 

 the vitelline and umbilical veins, and breaks up these vessels into a series of capil- 

 lary-like vessels termed sinusoids (Minot), which ramify in the meshes of the cellular 





