THE ABDOMEN 



805 



veins and bile-ducts. According to some authorities they send 

 minute capillary branches into the interior of each lobule to join 

 the intralobular plexus of the venae portae, but this view is not 

 held by others. 



The function of the hepatic artery and its branches is to nourish 

 the tissues of the liver, whilst the portal blood suppUes the materials 

 which are elaborated by the hepatic cells. 



The hepatic veins commence in the centre of each lobule as 

 an intralobular or central vein. The intralobular veins open into 

 the suhlohular veins, which are 

 closely adherent to the bases 

 of the lobules. The sublobular 

 veins join to form larger sub- 

 lobular veins, and these in turn 

 terminate in the hepatic veins, 

 which are not in direct contact 

 with the lobules. The hepatic 

 veins pass to the caval fossa 

 on the posterior surface of the 

 liver, towards which they con- 

 verge, taking up sublobular 

 veins in their course. The 

 passages which contain the 

 veins are known as the hepatic 

 canals. On arriving at the 

 upper part of the caval fossa 

 they are reduced to two or 

 three in number, which pour 

 their contents directly into the 

 inferior vena cava. It is to 

 be noted that the hepatic veins 

 converge to the caval fossa on 

 the posterior surface, whilst the 

 branches of the vena portae radiate in all directions from the portal 

 fissure. The hepatic veins are accompanied only by lymphatic 

 vessels, and are surroimded by a very scanty amount of areolar 

 tissue, which explains why they present open mouths when cut across. 



Distinguishing Characters of the Hepatic and Portal Veins — Hepatic Veins. 



— (i ) These present open mouths when cut across. (2) They are accompanied 

 only by Ij-mphatic vessels. (3) Their waUs are very thin, and are practically 

 in direct contact Avith the substance of the liver. {4) They converge towards 

 the caval fossa on the posterior surface. 



Portal Veins. — (i) The mouths of these veins are practically closed or 

 collapsed when cut across. (2) The veins are accompanied by branches of 

 the hepatic arter\', and by ducts. (3) Their walls are fairly tliick, and are 

 separated from the substance of the Uver by the sheaths derived from Glisson's 

 capsule. (4) They radiate in all directions from the portal fissure in portal canals. 



Hepatic Cells. — ^These are situated within the lobules. They are 

 polj'hedral. granular cells, having a diameter of ybW inch, and 

 each contains a round nucleus. They have no cell-wall, properly 



Fig. 346. — Two Hepatic Lobules 

 (highly magnified). 



A, Lobule showing the Intralobular 

 Plexus ; B, Lobule showing the 

 Hepatic Cells. 



