Studies of the Lymphatics of the Liver and the Uptake of Interstitital Fluid From the Space of Disse

Morphology

Al-Jomard, Rashid

University:University of Glasgow

关键词: Morphology;   

Others  :  http://theses.gla.ac.uk/77589/1/10997372.pdf

来源: University of Glasgow

【 摘 要 】

SUMMARY 1. It is generally agreed that the liver produces a substantial amount of lymph. In fact it is the largest single source of lymph in the body, contributing 15-20% of the total. This hepatic lymph is largely originating from the interstitial fluid in the space of Disse. However, it is still not clear how the fluid in the space of Disse may end up in the lymphatics of the portal tracts, as lymphatic vessels were not seen to penetrate into the hepatic lobules. 2. This study aimed to investigate the route followed by interstitial fluid from Disse's space to the lymphatic vessels of the portal tracts. The livers of adult Albino swiss rats, fixed by vascular perfusion, were studied by light and electron microscopy. 3. Frequent gaps were found between hepatocytes of the perilobular limiting plate. They were often independent of vessels entering the lobule. These were usually wider than the space of Disse, and contained hepatocytic microvilli, bundles of collagen fibres, and occasional slender fibroblastic processes extending into the lobule from portal tract interstitiurn. Large gaps (32 jum wide or more) allowed the sinusoidal endothelium to abut directly on portal tract interstitium. These gaps allowed free communication between the space of Disse and portal tract interstitium. 4. In the periportal connective tissue, long flattened processes of mesenchymal cells or fibroblasts formed incomplete linings of well defined spaces, which contained precipitated protein and occasional leukocytes. The lining cells were often associated with collagen fibres. The discontinuities in the wall of these spaces were confirmed by S.E.M. These mesenchymal/fibroblastic "channels" were seen in the perilobular space of Mall, in the interstitium of portal tracts and in proximity to lymphatics. They were not true lymphatics, but appeared to function as prelymphatic channels, leading the protein-rich interstitial fluid to adjacent terminal Lymphatics, from which they could be distinguished, but only by T.E.M. 5. In the light of all these findings, it is suggested that interstitial fluid in Disse's space had found its way through gaps in the perilobular limiting plate to reach the perilobular space of Mall, from which it drained by mesenchyma1/fibrob I astic preLymphatics to reach the initial lymphatics. 6. This hypothesis was tested by studying the distribution, in the liver, of several artificial and natural tracers introduced into the circulation of the artificial tracers, ferritin, Pontamine Sky Blue and Monastral Blue. Ferritin and Pontamine Sky Blue were identified by T.E.M. at all points along the proposed pathway. Most of the Monastral Blue particles were phagocytised. Natural tracers - chylomicrons and Lipoproteins - introduced by feeding the animals with a high fat diet, were also found to be distributed along the proposed pathway. 7. Lymphatic profiles were found in only about 50% of portal tracts of adult rats Livers. They did not accompany every branch of the portal tree, and when they did, they stopped short of the terminal twigs; lymphatic profiles were not seen in portal tracts whose associated portal vein branch diameter was 30-40 urn or less. In 100 portal tract profiles it was found that in 44.4% lymphatics were related equally to both arteries and veins, 32% mainly to veins and 22.8% to arteries. it was also found that 67% of portal tracts' profiles (mainly in small, peripheral, portal tracts) had a single lymphatic, 19% had 2, 8% had 3, 4% had 4, 1% had 5 and 1% had 6. Multiple lymphatic profiles were mainly found in large portaL tracts. This suggests that lymphatics in rat liver are principally in the form of trunks and not in the form of a plexus. 8. The histogenesis and topographic distribution of lymphatics in the livers of groups of Albino-swiss rats aged 24 hours, 1,2,3 weeks and adults were studied by optical and T.E.M. At 24 hours, lymphatics were found in only about 2% of sectional profiles of portal tracts, only in association with the largest branches of the portal vein. At 1 week, lymphatics were found in portal tracts further from the porta hepatis, associated with portal vein branches down to 60 urn in diameter. At 2 weeks, lymphatics were found in 15% of tracts, at 3 weeks in 30% and in adults in 50% of portal tracts. This statistical evidence suggests that Lymphatics develop by centrifugal extension from the porta hepatis accompanying many branches of the portal vein. The E.M. evidence indicated that this extension occured mainly by the differentiation, in situ, of mesenchymal cells, and their progressive assimilation by the tips of the lymphatic tree. Frequent examples were found of small lymphatics lined by typical endothelium ending open-mouthed in continuity with mesenchymal cells bounding irregular fluid filled tissue spaces.(Abstract shortened by ProQuest.).