The gastrointestinal tract (GIT) is a long tubular structure starting at the mouth and extending up to the anus, with the primary digestive organs being located intra-abdominally. Due to its important role in digestion, absorption and elimination of food and waste, the GIT has a rich arterial blood supply with intramural and extramural parts. Extramural arterial supply for the esophagus comes from the thoracic aorta and its branches, while the abdominal organs are supplied by three unpaired arteries, which originate from the abdominal aorta. The arterial supply of the GIT is derived embryologically from the arteries of the foregut, midgut and the hindgut. The arterial vasculature of the GIT has clinical and surgical value as there is significant blood supply, anatomical variation, anastomoses between the branches and also due to the occurrence of ischemic colitis following thrombosis in the celiac-mesenteric trunk.
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superior mesenteric artery diagram

Image: “The superior mesenteric artery and its branches.” by Henry Vandyke Carter, Henry Gray (1918) “Anatomy of the Human Body”. Gray’s Anatomy, Plate 534. License: Public Domain

Embryology of the GI Tract

The GIT is derived embryologically from the foregut, midgut and hindgut, with their corresponding neurovascular supply. Developmentally, the oral cavity is formed with the loss of the buccopharyngeal membrane, while the pharynx originates from the pharyngeal arches. The next section of the foregut, after the oral cavity, is the primitive pharynx, followed by a single esophagotracheal tube, which lies dorsal to the primitive heart.

During the fourth week of embryonic life, the primitive gut develops from an out-pouching of the yolk sac, which is a structure lined by endoderm.

The primitive gut gives rise to the foregut, midgut and hindgut. The foregut is the precursor from which develop the esophagus, the stomach and the first and second part of the duodenum, liver, gallbladder as well as the superior part of the pancreas. All these organs are supplied by the branches of the artery of the foregut, the celiac trunk.

The midgut gives rise to the third part of the duodenum, the jejunum, ileum, cecum, appendix, ascending colon and the right two-thirds of the transverse colon. These are supplied by the branches of the artery of the midgut, the superior mesenteric artery.

The hindgut gives rise to the left one-third of the transverse colon, descending colon, rectum and upper part of the anal canal. These structures are supplied by the branches of the artery of the hindgut, the inferior mesenteric artery.

Abdominal Aorta

This major artery begins as a continuation of the thoracic aorta at the aortic hiatus of the diaphragm at the level of the T12 vertebra. It ends by bifurcating into the common iliac arteries at the level of the L4 lumbar vertebra.

Three anterior branches arising from the abdominal aorta supply the gut. From superior to inferior, their names are the celiac trunk, the superior mesenteric artery and the inferior mesenteric artery. These three branches are individual entities and their terminal branches anastomose.

Celiac Trunk

celiac artery gray533

Image: “The celiac artery and its branches; the stomach has been raised and the peritoneum removed.” by Henry Vandyke Carter, Henry Gray (1918) “Anatomy of the Human Body”. Gray’s Anatomy, Plate 533. License: Public Domain

The celiac trunk is an important artery from a surgical stand point. It originates from the abdominal aorta and lies in the transpyloric plane at the upper border of the L1 vertebra.

The artery branches out into the splenic artery, the left gastric artery and the common hepatic artery. The celiac trunk and its branches supply oxygenated blood to the abdominal esophagus, the stomach, the first and second part of the duodenum, liver, gallbladder, spleen and the superior part of the pancreas.


Branches of the celiac artery … and their branches
1. Left gastric a. Branch to stomach and esophagus
2. Common hepatic a. Right gastric a., gastroduodenal a., proper hepatic a.
3. Splenic a.
Short gastric a., left gastro-omental a., dorsal pancreatic and greater pancreatic a.

Table 1: Branches of the celiac trunk

Superior Mesenteric Artery (SMA)

This midgut artery originates from the abdominal aorta .Its origin lies at the level of the L1 vertebra. It then runs anteroinferiorly, behind the splenic vein and the neck of the pancreas. During this part of its journey, it is separated from the aorta by the following structures:

  • Third part of the duodenum and part of the small intestines, which may be compressed by the SMA, causing the superior mesenteric artery syndrome.
  • Pancreatic uncinate process, which hooks around the SMA.
  • The left renal vein, which travels from the left kidney to the inferior vena cava and can be compressed here by the SMA and the abdominal aorta, causing the nutcracker syndrome.

The SMA  branches into the intestinal arteries, the inferior pancreaticoduodenal artery, the ileocolic artery and the right and the middle colic arteries. These supply the organs of the midgut, namely the third part of the duodenum, the jejunum, ileum, cecum, appendix, ascending colon and the right two-thirds of the transverse colon.

Inferior Mesenteric Artery (IMA)

colonic blood supply

Image: “Colonic blood supply. 1 – transverse colon, 2 – ascending colon, 3 – caecum, 4 – right colic artery, 5 – appendix, 6 – middle colic artery, 7 – Cannon-Böhm point (the border between the areas of SMA and IMA supplies) , 8 – superior mesenteric artery, 9 – marginal artery, 10 – ileocolic artery, 11 – jejunum (partial), 12 – ileum (partial). Proximal small intestine, abdominal organs (pancreas, liver etc), sigmoid and rectum, aorta and inferior mesenteric artery are not shown. Pink – supply from superior mesenteric artery (SMA) and its branches: middle colic, right colic, ileocolic arteries. Blue – supply from inferior mesenteric artery (IMA) and its branches: left colic, sigmoid, superior rectal artery.” by Filip em – Own work based on PD image from Gray’s Anatomy (Image:Gray534.png). Other sources: Schumacher Topographische Anatomie des Menschen (Polish transl., Volumed 1994); Moore & Agur, Essential Clinical Anatomy, 3rd Ed 2007. This vector image was created with Inkscape. License: CC BY 3.0

This artery of the hindgut arises from the abdominal aorta, inferior to the superior mesenteric artery at the level of the L3 vertebra. It is the smallest branch among the three anterior branches of the abdominal aorta.

Initially, it descends anterior to the abdominal aorta, and then crosses to the left as it continues to descend. It gives off the following branches: the left colic, two to three sigmoid branches and the superior rectal artery, which is a terminal branch. These supply oxygenated blood to the left one-third of the transverse colon, descending colon, rectum and superior part of the anal canal.

Branches of the SMA and IMA anastomose to form the marginal arteries of Drummond and the Riolan’s arcade (anastomoses between the left colic and medial colic artery). Thus, they provide abundant oxygenated blood to the colon, except for certain watershed areas with poor blood supply, e.g., splenic flexure of the colon.

The marginal artery runs distal, while the arc of Riolan (also known as the meandering mesenteric artery) runs proximal to the root of the mesentery. The terminal branches of the right colic, middle colic, left colic and sigmoid branches enter the colonic wall and are called the vasa recta.



Clinical Relevance of the Abdominal Arteries

Celiac trunk

(All this is not relevant to step 1)

This artery is an important source of oxygenated blood to the foregut structures as the various anastomotic networks with other major arteries in the region do not provide adequate perfusion. Therefore, in a living individual, the artery cannot be ligated safely as its occlusion leads to necrosis of the various tissues that it supplies. This is essential to remember during surgical procedures of the foregut.

Variations in the celiac trunk   (All this is not relevant to step 1)

As mentioned, the celiac trunk is an important artery, and its anatomy has surgical significance. Variations in its pattern of branching are seen in approximately 15% of the population. Knowledge about these variations is important for diagnostic and surgical abdominal procedures. Otherwise, there is a high risk of surgical errors, which may lead to possible lethal complications.

Celiac artery compression syndrome

This syndrome, also called Dunbar syndrome, is a condition characterized by abdominal pain associated with meals, weight loss and abdominal bruit. It is a result of the external compression of the celiac artery and celiac plexus by the median arcuate ligament.

It is diagnosed clinically after excluding other causes of abdominal pain. The diagnosis can be confirmed with ultrasound, CT scan or MRI. Treatment is usually surgical excision of the constricting median arcuate ligament and the celiac ganglion.

Superior mesenteric artery syndrome

This is a rare syndrome and is caused by the compression of the last part of the duodenum by the SMA and the abdominal aorta. It has to be differentiated from celiac artery compression syndrome as well as nutcracker syndrome.

It is characterized by severe, stabbing, post-meal, abdominal pain, early satiety, nausea and vomiting. Early diagnosis is difficult but essential as delay can lead to severe dehydration, malnutrition, electrolyte abnormalities, etc. Treatment consists of medical management and, in severe cases, surgical bypass.

Nutcracker syndrome

nutcracker syndrome ct scan

Image: “Compression of the left renal vein (marked by the arrow) between the superior mesenteric artery and the aorta due to nutcracker syndrome.” by James Heilman, MD – Own work. License: CC BY-SA 3.0

This syndrome is characterized by hematuria and left flank pain due to compression of the left renal vein between the abdominal aorta and the SMA.

In the saggital or transverse plane, the abdominal aorta and the SMA appear like a nutcracker with a nut (the left renal vein) in its jaws, hence the name. The diagnosis of the syndrome is usually confirmed with left renal venography. Treatment consists of endovascular stenting/renal vein re-implantation depending on the severity of the symptoms.

Superior mesenteric artery thrombosis

The SMA is rarely affected by atherosclerosis. However, in rare cases, especially following atrial fibrillation or myocardial infarction, the artery may get occluded by a thrombus leading to ischemic colitis.

This usually occurs in the watershed areas like the splenic flexure and is characterized by acute onset abdominal pain and blood in the stools. In most cases, there is a history of recent myocardial infarction or atrial fibrillation. The condition may occur acutely or over a period of time (chronic ischemia). Diagnosis is confirmed with mesenteric angiography and definitive treatment consists of emergency laparotomy with bowel resection–anastomoses.

Chronic ischemic colitis

When blood flow to parts of the colon is reduced due to arterial blocks or thrombus, the colon may become inflamed and eventually gangrenous. In such situations, we may find the marginal artery and the arc of Riolan significantly enlarged in an attempt to perfuse the ischemic colonic segment.

Left hemicolectomy

This surgical procedure involves the removal of the left side of the large bowel, usually necessary in case of tumors. The IMA and its branches have to be resected during this surgery as the IMA supplies the left colon.

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