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Updated: 03/13/08 12:38 PM
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Figure 7
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Colon is supplied by two major arteries
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The small intestine and the proximal half of the colon (to midtransverse) derives from the embryonic midgut and appropriately receives its blood supply from the superior mesenteric artery. The distal-half of the colon derives from the hindgut and receives its supply from the inferior mesenteric artery. The various colic arteries from both the superior and inferior mesenteric vessels divide into two divergent branches as they approach the gut and each branch runs parallel to the gut as marginal arteries which anastomose with one another. If there is a weak link in this marginal system, it is usually between the middle and left colic arteries which supplies the colon in the region of the splenic flexure. This accounts for the frequency of splenic flexure involvement by ischemia or infarction when blood supply is impaired by arteriosclerosis or some other cause. The venous drainage follows similar pathways and ultimately drains via the portal vein into the liver. The lower rectum and anal canal are invested by the internal and external hemorrhoidal complexes which are drained by the middle and inferior hemorrhoidal veins which ultimately communicate with both the portal vein and the vena cava. In portal hypertension due to liver disease or portal vein obstruction, back pressure is readily transmitted to form prominent dilated anorectal veins; it is via this pathway that some of the excess portal blood drains back to the heart via the vena cava.
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Next Sections: (E) Lympatics & (F) Nerve Supply »
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| © Copyright University of Washington Division of Gastroenterology 1999-2008
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