Appendicular artery and the mesoappendix

The appendicular artery is the main arterial supply of the appendix, which hangs from the terminal ileum (the last part of the small intestine) on its own small fold, the mesoappendix. It usually arises from the ileocolic artery, and the ileocolic artery comes from the superior mesenteric artery, the artery of the midgut. The midgut is the part of the embryonic gut tube that gives rise to the small intestine, the appendix and the first part of the colon.

The artery runs in the mesoappendix, the appendix's own small mesentery. A mesentery is a fold of peritoneum (the thin membrane lining the abdominal cavity) that anchors a section of bowel and carries its vessels. The mesoappendix suspends the appendix from the terminal ileum and holds the appendicular artery, the appendicular vein and the lymphatic vessels. Venous blood drains to the superior mesenteric vein, and lymph drains to the ileocolic nodes around the ileocolic artery. 'Meso-' means mesentery, so the mesoappendix is the mesentery of the appendix.

Because the appendix is a midgut structure, its supply comes from the superior mesenteric system and not from the inferior mesenteric artery, which is the artery of the hindgut (the left side of the colon). The right colic artery supplies the ascending colon and the middle colic artery the transverse colon, so neither is the vessel of the appendix.

The ileocolic origin is usual rather than invariable. In one dissection series the main appendicular artery arose from the ileocolic artery in 80% of specimens, and an accessory (extra) appendicular artery was present in 13%.

At appendicectomy (surgical removal of the appendix) the surgeon divides the mesoappendix, most often with diathermy (heat used to seal vessels) or clips, and so controls the appendicular artery within it.