welcome to section five of cardiovascular anatomy in this section we will discuss the gastrointestinal arteries when you think of the gastrointestinal arteries it's best to break it up into three components the foregut the mid gut and the hind gut the four gut is supplied by the celiac trunk and these four gut structures include the lower esophagus the stomach and the first part of the duodenum the second portion the mid gut is supplied by the superior mesenteric artery and these mid gut structures include these small intestines the a sending colon and the proximal two-thirds of the transverse colon the third portion the hindgut is supplied by the inferior mesenteric artery or ima hind gut structures include the distal 1/3 of the transverse colon the descending and sigmoid colon as well as the rectum here is an image depicting the arterial supply of the GI structures this can be found in your text in section 5 of the cardiovascular anatomy chapter here we can see the foregut labeled it's everything above this line and we can see that the celiac trunk is what supplies all of these structures and we'll dive into this more in a moment next look at the mid gut this is supplied by everything below this line and above this line and as we mentioned on the previous slide this includes the colon up to the proximal two-thirds of the transverse colon right here finally let's look at the hindgut and this is everything that is below this line and above this line now focusing on the arterial supply of the hindgut we can see that the inferior Muse enteric artery actually supplies the hindgut structures and going to the mid gut we see that the superior mesenteric artery supplies these structures and lastly the foregut we can see that the celiac trunk supplies all these structures and we'll dive into that more in a moment arterial structures for the GI system are super important and have many clinical tie-ins for that reason we will dive in to more details on the celiac trunk the superior Muse enteric artery and the inferior mesenteric artery so we're gonna start with a silly act trunk as the aorta descends down it gives rise to the celiac trunk and then as you go further it gives rise to the superior mesenteric artery and further down from that we get the inferior mesenteric artery but let's zoom up on the celiac trunk the celiac trunk is labeled here it has three main branches the left gastric artery the splenic artery and the common hepatic artery from these three branches the celiac trunk supplies blood to the spleen the foregut structures and liver now let's focus our attention only on the common hepatic artery now the common khari gives rise to the hepatic artery proper which then supplies the liver this figure is discussed in great detail in GI physiology right now I want to draw your attention to the hepatic artery proper this supplies the liver and it branches from the celiac trunk as we just mentioned now this particular image is simplified and does not show the celiac trunk but just keep this in mind the next item to keep in mind is that the hepatic artery proper is one of three structures that forms the portal triad as you can see here this triad is split into multiple tiny branches little tiny triads and ultimately the hepatic vein drains the deoxygenated blood and takes it to the IVC and going back to this image we can see that the common hepatic artery branches into the hepatic artery proper and the gastro do one laundry notice that this gastro drawn artery right here passes posterior to the duodenum this is a very significant point and that's because peptic ulcers can form in the stomach and the duodenum now ulcers are most common in the duodenum but they're usually anterior in rare circumstances ulcers can form on the posterior surface and it's with reference to these posterior duodenal ulcers that the gastro delano artery is relevant and that's because ulcers can potentially perforate the entire thickness of the duodenum wall and if this gastroduodenal artery is unlucky enough to be on the other side of the ulcer when it perforates the duodenum it can bleed not just bleed but hemorrhage uncontrollably this is an extremely dangerous complication of posterior duodenal ulcers going back to the table we have identified the three main branches the left gastric artery the common hepatic artery and the splenic artery and we just mentioned that the gastro duodenal artery can hemorrhage with posterior duodenal ulcers and the hepatic artery proper is a part of the portal triad now let me draw your attention to the splenic artery this is a branch of the celiac trunk and it goes all the way back posterior to the stomach and reaches the spleen the third and final branch of the celiac trunk is the left gastric artery which comes up and you can see supplies the superior most portion of the stomach specifically this lesser curvature right here now going back to the table we've identified these three main branches the left gastric artery and the common hepatic artery and the splenic artery and of course the celiac trunk supplies the foregut and the spleen via the splenic artery and the liver via a branch of the common hepatic artery which is the hepatic artery proper if you look to the column on the far right you can see that the product artery proper forms part of the portal triad within the liver in a high-yield pearl is that the gastroduodenal artery can hemorrhage with posterior duodenal ulcers and we identified the left gastric artery but we need to discuss the right gastric artery and how both the right and left arteries can hemorrhage with gastric ulcers now gastric ulcers are those in the stomach are not as common as duodenal ulcers when they do occur they form on the lesser curvature of the stomach and what arteries supply the lesser curvature the left gastric artery and the right gastric artery which is a branch of the common hepatic artery now both gastric arteries form an anastomosis right here to supply blood to the entire lesser curvature if there is an ulcer on this lesser curvature and it perforates hemorrhage to one or both of these arteries at the left or right Yaser artery can occur so again stomach ulcers can hemorrhage the left and right castor Carter II now this last item regarding the gastric fundus we will approach in a moment first let's do a question to apply what you've learned so far a 47 year old male presents with worsening upper abdominal pain endoscopy of the stomach is performed and reveals an ulcer in an area where gastric ulcers are most likely to present if this ulcer were to perforate what arterial vessel is susceptible to injury in this patient with a gastric ulcer hopefully you noticed that the ulcer is located on the lesser curvature of the stomach and the clue telling us it was on the lesser curvature is the line where it says that the ulcer occurs in an area where gastric ulcers are most likely to present and what vessels are located in a lesser curvature the right and left gastric artery x' and it is these that are susceptible to hemorrhage in a gastric ulcer perforation again these are located right here so a gastric ulcer can perforate these arteries now let's talk more about the splenic artery notice on this image how the splenic artery has several branches it has the short gastric artery which supplies the fundus of the stomach it also has the left gastroepiploic artery which forms an anastomosis with the right gastroepiploic artery which ultimately originates from the gastro 2 artery now the splenic artery also sends some branches to the pancreas and the posterior stomach but don't get wrapped up in those arteries the main thing i want you to know is that it's this short gastric artery that supplies the fundus it's really the only way that the fundus gets oxygenated blood and what this means is that the gastric fundus heavily relies on the splenic artery whereas the greater curvature of the stomach has an anastomosis which means it receives some blood from the left gastric artery from the splenic artery and some from the gastro tunnel artery which gives rise to the right gastroepiploic artery the point is is that the splenic artery is vital to the fundus not necessarily to the greater curvature so going back to this table if there is gastric fundus ischemia you can know that it's the splenic artery that's the problem usually occurring with splenic artery obstruction now let's move on to the superior mesenteric artery now the SMA branches off the aorta near the l1 vertebra level and it supplies blood to the mid get structures now here we have labeled these superior Muse enteric artery and this occurs around the l1 vertebral level and it supplies the mid gut which means it will supply the small intestine all the way down to the proximal two-thirds of the transverse colon now notice how the duodenum crosses the aorta right here but it does so behind the SMA this is extremely important and I will explain why the part of the duodenum that crosses here is the third portion of the duodenum and normally there is this fat pad surrounding the duodenum preventing the SMA from squeezing down on to the duodenum and we've demonstrated that here with this yellow triangle if this fat pad has diminished which can occur for a variety of reasons including malnutrition anorexia or cancer and then the duodenum can be squished leading to a small bowel obstruction and this is called SMA syndrome now we've just discussed how the SMA can negatively impact the third portion of the duodenum but how can the third portion of the duodenum negatively impact the SMA well let's say a patient has a cancer in his third part of the duodenum and it greatly enhances the diameter this causes the duodenum to press up against the SMA potentially occluding it leading to ischemia of downstream structures and these structures supplied by the SMA or of course mid get structures so going back to our table with our discussion of SMA we've discussed SMA syndrome which is how the SMA can compress the duodenum causing an SBO we've also discussed how the third part of the duodenum can compress the SMA causing a C Mia now let's talk about how the SMA can compress another local structure the left renal vein like the third part of the duodenum the left renal vein crosses the aorta posterior to the SMA in order to drain into the IVC when the fat pad is diminished this vein can be compressed and this is called Nutcracker syndrome now let's find the left renal vein here which is clearly labeled and it crosses through this fat pad anterior to the aorta but posterior to the SMA and you might get SMA syndrome and Nutcracker syndrome mixed up but that is not important the anatomy is what is important know the anatomy and you will dominate your boards just remember that the third portion of the duodenum passes here as well as the left renal vein the last item for the superior museum Taric artery is acute is enteric ischemia this occurs when blood supply to the intestinal structures is blocked leading to ischemia of mid-calf structures since it applies to both the SMA and IMA we will discuss the IMA as part of this explanation now acute muse enteric ischemia is fairly simple if you block the SMA the mid get structures will experience ischemia so everything in this region and if you block the IMA all the hindgut structures from this line to this line will experience ischemia and by the way means enteric ischemia is very painful it kind of feels like a heart attack in the belly again acute muse enteric ischemia can occur with the superior muse enteric artery or the inferior muse enteric artery but acute muse enteric ischemia is far more common with the SMA than the IMA so now we've basically covered what you need to know for the IMA it supplies the hindgut and acute muse enteric ischemia can occur with occlusion of the IMA but just remember as I said before this is less common than the SMA now let's do one last question a 64 year old female presents with excruciating abdominal pain thorough evaluation reveals complete compression of the duodenum as it crosses the abdominal aorta which statement may be true regarding the pathological process hey there's increased fat storage surrounding the area of compression B arteries supplying the hindgut are responsible for the compressed structure C compression results in decreased venous drainage of the left kidney or D atherosclerosis is the cause of the intestinal obstruction now hopefully you notice from the question stem that the third part of the duodenum is compressed between the aorta and the SMA because we see that there is compression of the duodenum as it crosses the abdominal aorta now in addition to the third part of the duodenum being compressed the left renal vein can also be compressed and the cause of compression of either of these structures is decreased fat in the area and this allows the angle between the SMA in the aorta to decrease causing obstruction so which of the following statements is true now we know that a is wrong and that's because in this pathology we know that it's caused by decreased fat storage not increased fat storage now B is wrong because the SMA supplies mid guessed structures not high and get structures and we know we're dealing with the mid gut not hindgut because we're talking about the third part of the duodenum which is obviously a mid gut structure and we know that D is wrong because the pathology is not caused by atherosclerosis is caused by decreased fat storage in the area so that leaves us with C which is the correct answer compression results in decreased venous drainage of the left kidney and we know that's true because the left renal vein is one of the structures that crosses this area going back to this image we clearly see the superior mesenteric artery supplying the mid gut and it can compress the third part of the duodenum and the left renal vein and that concludes the section