The gastrointestinal tract extends from mouth to the rectum, and enables us to gain nutrients from the food we eat. Gut associated lymphoid tissue performs immunological function by eliminating bacteria and intraluminal toxin and protects the intestinal mucosa from invading pathogens. It has various parts that are specialized to absorb certain nutrients and vitamins e.g. vitamin B12 and bile salts are absorbed in the terminal ileum. The bowel develops in three separate sections, namely the foregut, midgut and hindgut supplied by separate nerves, arteries, and veins. This article will describe the celiac or coeliac trunk (which supplies the foregut), including its branches, and clinical relevance.
Anatomy of the Gastrointestinal Tract
Three major divisions of the gastrointestinal tract are foregut, midgut and hindgut. The foregut extends from the mouth to the major duodenal papilla (where the ampulla of Vater empties into the duodenum). The midgut extends from this point to two thirds of the way along the transverse colon. The hindgut runs from this point to the superior rectum.
The coeliac trunk (or celiac trunk) supplies the foregut, superior mesenteric artery supplies the midgut and the inferior mesenteric artery supplies the hindgut. The coeliac artery arises from the abdominal aorta as soon as it passes through the diaphragm at the level of the twelfth thoracic vertebrae. It gives off three major branches i.e. the left gastric, common hepatic and splenic.
In the same sense, the sympathetic input to the foregut, midgut and hindgut are supplied by the greater, lesser and least thoracic splanchnic nerves respectively. The parasympathetic input to the whole bowel as far as the splenic flexure is supplied by the vagus nerve (cranial nerve X).
Branches of the Celiac Trunk
Left Gastric Artery
This is the smallest and the first branch that arises from the coeliac trunk and passes into the lesser omentum (which connects the lesser curvature of the stomach to the liver) along the lesser curvature of the stomach, to supply its superior portion. Here it anastomoses with right gastric artery. Some branches of the left gastric artery also supply the inferior part of the oesophagus.
Common Hepatic Artery
This branch arises from the coeliac trunk and runs towards the right towards the liver and in order to enter the lesser sac. This artery gives off the right gastric artery above the first part of the duodenum, which runs between the peritoneal layers of lesser omentum to supply the lesser curvature of the stomach and anastomoses with the left gastric artery.
The common hepatic artery then divides into the hepatic artery proper and the gastroduodenal artery. At the porta hepatis the hepatic artery proper divides into the right and left hepatic arteries and enter the liver. These vessels then divide further into lobar arteries.
The gastroduodenal artery arises posterosuperior to the first part of duodenum, giving off the right gastroepiploic artery which supplies the greater curvature of the stomach. The gastroduodenal artery terminates as the superior pancreaticoduodenal artery, which supplies the head of the pancreas and the anterior and posterior surfaces of the duodenum. It anastomose with the inferior pancreaticoduodenal artery (first branch of the superior mesenteric artery).
This is a tortuous branch that runs towards the hilum of the spleen. On the way it has a number of arteries that supply the neck, body and tail of the pancreas. It also gives off the left gastroepiploic artery that supplies the greater curvature of the stomach, and anastomoses with the right gastroepiploic artery.
The splenic artery also gives off the short gastric arteries before it reaches the hilum of the spleen. It runs within the gastrosplenic ligament in order to supply the fundus of the stomach as well as the superior part of the greater curvature of the stomach. It anastomoses with the left gastric artery.
To summarize and have a clear picture in your mind, take a look at the following diagram illustrating the branches of the celiac trunk!
A peptic ulcer is an erosion in the mucosa of the stomach that commonly results from the presence of H.Pylori bacteria or the overuse of non-steroidal anti-inflammatory medications e.g. aspirin. If it becomes deep enough it may erode into a major vessel (commonly the left gastric artery) resulting in massive blood loss.
Splenic Artery Aneurysms
These are rare but are the third most common abdominal aneurysm (after aneurysms of the abdominal aorta and iliac arteries). High blood pressure and smoking are risk factors for aneurysm formation and the treatment of choice is percutaneous endovascular treatment, or an open operation if that is not possible. Aortic aneurysms are most commonly infrarenal (below the renal arteries).
The liver is a very vascular organ (as it is supplied by the hepatic arteries and the hepatic portal vein that carries the venous blood from the bowels). Hence, in order to reduce blood loss during liver surgery, the portal triad can be clamped. The portal triad consists of the common bile duct, the hepatic artery proper and the hepatic portal vein.
Coeliac Artery Compression Syndrome
The median arcuate ligament is a part of the diaphragm, and it forms the crura of the diaphragm on either side of the abdominal aorta as it passes through the diaphragm. The insertion point of this ligament may be too low in some people, leading to compression of the coeliac trunk. This can result in epigastric pain resulting from the ischaemia, weight loss and abdominal bruit. Treatment includes surgical decompression that is usually performed via laparoscopic (keyhole) operation.