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CHAPTER 42 



The flow of blood in the mesenteric vessels' 



EUGENE GRIM Department oj Physiology, University of Minnesota, Minneapolis, Minnesota 



CHAPTER CONTENTS 



Magnitude of Total Mesenteric Blood Flow 

 Partition of Total Blood Flow 



Major Organs 



Individual Tissues 



Vessels of Different Sizes 

 Mesenteric Blood Volume 

 Factors Affecting the Blood Flow and Its Distribution 



Stomach 



Intestine 



Pancreas 



Spleen 



Mesenteric Circulation as a Whole 

 Relation of Blood Flow to Function of the Mesenteric Organs 



the mesenteric circulation is usually considered to 

 be that part of the systemic circulation which sup- 

 plies the stomach, small intestine, large intestine, 

 pancreas, and spleen. These organs receive blood 

 from all the branches of the celiac (except the hepatic 

 proper), the superior mesenteric, and the inferior 

 mesenteric arteries. They are not drained directly 

 into the venous system as are most organs, but into 

 the portal vein from which the blood passes through 

 a second set of capillaries in the liver before entering 

 the inferior vena cava. 



Because of the peculiar anatomy of this venous 

 drainage system, the flow of blood in the mesenteric 

 vessels may be altered profoundly by factors which 

 do not act directly on these vessels but rather change 

 the resistance of the hepatic vasculature. This poses a 

 problem for the investigator who uses the intact 

 animal as the most "physiological" subject for study. 



1 This chapter was written during the tenure of a U. S. 

 Public Health Service Senior Research Fellowship (SF-161). 



Great care must be exercised in the interpretation of 

 the results of such studies, particularly when they 

 disagree with those from investigations on the iso- 

 lated mesenteric organs. 



The mesenteric circulation as such has not pre- 

 viously been the subject of a comprehensive review, 

 although it has been considered in a subsidiary 

 fashion in reviews on the total splanchnic blood flow 

 by such authors as La Croix (92) and Bradley (21). 

 Even the standard textbooks of physiology, in which 

 can be found sections devoted to the circulation 

 through the heart, brain, lungs, kidneys, liver, and 

 skeletal musculature, contain few statements con- 

 cerning the circulation through the mesenteric 

 organs. 



In part, the cause of this is the relative scarcity of 

 quantitative information on the subject and the 

 many instances in which different investigators have 

 published contradictory results. For the same reasons 

 many of the statements that follow should be taken 

 as tentative. This review might be better viewed as 

 indicating guide lines for future research rather than 

 as a definitive dissertation. 



MAGNITUDE OF TOTAL MESENTERIC BLOOD FLOW 



The total flow of blood through the mesenteric 

 system can be most directly determined by measuring 

 the flow through the portal vein. Since there has 

 been no suitable method for this measurement in the 

 human, all the available quantitative information 

 has been obtained in experimental animals, especially 

 the dog. 



One of the earliest measurements of portal venous 

 flow was made by Burton-Opitz (30) as a part of 



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