The Intestinal Blood Supply

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The blood supply to the intestines involves three major arteries and many smaller arteries, which fan out throughout the abdominal region. These arteries work together to supply the intestines with a vital supply of oxygenated blood.

Anatomy

Oxygenated blood leaves the heart through the aorta, which descends into the abdominal cavity as the abdominal aorta. The abdominal aorta forms several branches, three of which supply blood to the intestines: the celiac trunk, superior mesenteric artery, and inferior mesenteric artery. Each of these arteries forms many smaller branches that spread throughout the abdomen to specific regions of the intestines. Unlike the other branches of the abdominal aorta, the three arteries that supply the intestines are unpaired arteries and extend from the anterior wall of the aorta.

Celiac Trunk

The celiac trunk extends from the abdominal aorta just inferior to the diaphragm and divides into three branches. One of these branches, the hepatic artery, further divides into three more branches to supply blood to the digestive organs. Of these branches, the gastroduodenal artery supplies blood to the pylorus of the stomach and the nearby duodenum of the small intestine.

Superior Mesenteric Artery

The superior mesenteric artery branches from the abdominal aorta inferior to the celiac trunk and provides oxygenated blood to most of the small intestine and the proximal large intestine. It forms five major branches to provide blood flow to many feet of intestines.

• The inferior pancreaticoduodenal artery is the first and smallest branch, which provides blood to the pancreas and the distal end of the duodenum.
• Next are the intestinal arteries, which can be divided into the jejunal and ileal groups. The jejunal arteries feed the tissues of the jejunum and form a network of interconnected arches throughout the mesentery. Blood to the ileum is provided by the ileal arteries, which form several tiers of interconnected arches in the mesentery before reaching the ileum. These arches provide detours for blood to prevent interruptions to the blood flow to the intestines.
• The next branch of the superior mesenteric artery, the ileocolic artery, provides blood to the terminal ileum, cecum, and appendix. It is followed by the right colic artery, which provides blood flow to the ascending colon.
• Finally, the middle colic artery forms the final branch of the superior mesenteric artery and provides blood flow to the transverse colon.

Inferior Mesenteric Artery

The inferior mesenteric artery splits from the abdominal aorta inferior to the superior mesenteric artery. It divides into three branches to provide blood to the large intestine. The left colic artery provides blood to the tissues of the descending colon, while the sigmoid artery provides blood to the sigmoid colon. Blood flowing to the superior regions of the rectum is provided by the superior rectal artery, which supplies the rectum to the level of the internal anal sphincter.

Blood flow to the rectum and anus below the internal anal sphincter is distinct from the blood flow to the other regions of the intestines. Below this point, blood is provided to the anus by the middle and inferior rectal arteries, which branch from the internal iliac arteries in the pelvis. This change in blood flow pattern is related to the embryonic development of this region, with the anus representing the border between the internally located endodermal tissue and the external ectodermal tissue.

Physiology

Many anastomoses, or communicating openings, form between the various arteries that provide blood to the intestines. These structures serve to prevent interruptions of blood flow to the intestines. For example, the right, middle, and left colic arteries form anastomoses to ensure the continuous flow of blood to the large intestine in the case of one of these arteries becoming blocked. Interruption of arterial blood flow quickly leads to tissue death in the intestines, a potentially fatal condition if not quickly detected and treated.