Blood supply of Alimentary tract

2. Blood supply of Alimentary tract

7. Oral cavity

8. Hard palate

9. Tongue

10. Oropharynx

11. Soft palate

12. Oesophagus

15. Arterial supply to the gastrointestinal tract • derived from the anterior midline visceral branches of the aorta • usually three anterior branches, the coeliac trunk and the superior and inferior mesenteric arteries

17. The coeliac trunk and its branches • supply from the distal third of the oesophagus to the mid part of the duodenum and all derived adenexae 1. liver, 2. biliarytree, 3. spleen, 4. dorsal pancreas, 5. greater omentum and lesser omentum).

18. The superior mesenteric artery • supplies the tract from the mid second part of the duodenum to the distal third of the transverse colon (jejunum, ileum, caecum, appendix, ascending colon and ileal mesentery).

19. The inferior mesenteric artery • supplies the tract from the distal transverse colon to the upper anal canal.

20. Anastomosesbetween the vascular territories around the head of the pancreas and the duodenum between • the anterior and posterior superior pancreaticoduodenal arteries and the inferior pancreaticoduodenalarteries

21. the posterior superior pancreaticoduodenal artery and jejunal arteries • the greater pancreatic artery and jejunal arteries

22. the posterior superior pancreaticoduodenal artery and jejunal arteries • the greater pancreatic artery and jejunal arteries

23. The anastomoses between the territories of the superior and inferior mesenteric arteries are less pronounced and more variable: • the most reliable is the pericolic marginal artery, which runs along the transverse colon.

26. Arterial anastomoses of the stomach • between the oesophageal arteries originating from the thoracic aorta and the vessels that supply the fundus in the region of the cardiac orifice..

27. At the pyloric orifice -some anastomosis between vessels of superior mesenteric artery origin and the pyloric vessels • The major named vessels supplying the stomach form extensive arterial anastomoses both on the serosal surface and around the curvatures.

28. The right and left gastroepiploic arteries and the left and right gastric arteries anastomose freely with each other along the greater and lesser curvatures respectively.

29. Anastomoses also form between the short gastric and left gastric arteries in the region of the fundus, and between the rightgastric and rightgastroepiploic arteries in the region of the antrum. • .

30. In addition to the extensive serosalanastomoses, networks form within the stomach wall at intramuscular, submucosal and mucosal levels

31. A true plexus of small arteries and arterioles is present within the submucosa • It supplies the mucosa and shows considerable regional variation both in the gastric wall and in the proximal duodenum.

32. The rich arterial supply to the stomach ensures that the high mucosal blood flow required for physiological functioning is maintained even if one or more vessels become occluded • The stomach exhibits considerable resistance to ischaemia even when multiple arterial supplies are lost.

39. Arterial anastomoses and the marginal artery of the colon • The marginal artery (of Drummond) of the colon is the name given to the vessel which lies closest to and parallels the wall of the large intestine. • Formed by the main trunks, and the arcades arising from, the ileocolic and right colic, middle colic and left colic arteries.

41. It is most apparent in the ascending, transverse and descending colons • The sigmoid colon has little if any marginal artery.

42. Anastomoses form between the main terminal branches which run parallel to the colon within the mesentery and give rise to vasa recta and vasa brevia to supply the colon.

43. The arc of Riolanis the name given to the arterial anastomosis which is sometimes present in the mesentery between the right side of the transverse colon and the upper descending colon.

44. When present it is formed from a large branch of the middle colic artery which runs parallel and posterior to the middle colic artery in the transverse mesocolon and anastomoses with an ascending branch of the left colic artery close to its origin in the root of the mesentery.

45. This provides a direct communication between the superior and inferior mesenteric arteries.

46. Colonic vascular occlusion • The marginal artery of the colon may become massively dilated when there is chronic, progressive occlusion of the superior mesenteric artery

47. under these conditions it is required to supply the majority of the midgut (except the proximal portion which is supplied by collateral vessels from the coeliac artery).

48. Occlusion of the inferior mesenteric artery does not always result in irreversible ischaemia of the descending and sigmoid colon, because the marginal artery of the colon usually receives an adequate supply from the left branch of the middle colic artery

49. Moreover, the sigmoid arteries may be supplied by the superior rectal artery, which anastomoses with the middle and inferior rectal arteries. • When ischaemia does occur, it is usually maximal in the proximal descending colon because this region is furthest from the collateral arterial supplies.