In
human anatomy, the superior mesenteric artery (SMA) is an
artery
An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the pul ...
which arises from the anterior surface of the
abdominal aorta, just inferior to the origin of the
celiac trunk
The celiac () artery (also spelled ''coeliac''), also known as the celiac trunk or truncus coeliacus, is the first major branch of the abdominal aorta. It is about 1.25 cm in length. Branching from the aorta at thoracic vertebra 12 (T12) i ...
, and supplies blood to the
intestine from the lower part of the
duodenum through two-thirds of the
transverse colon
In human anatomy, the transverse colon is the longest and most movable part of the colon.
Anatomical position
It crosses the abdomen from the ascending colon at the right colic flexure (hepatic flexure) with a downward convexity to the descend ...
, as well as the
pancreas
The pancreas is an organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine gland, i.e. it has both an end ...
.
Structure
It arises anterior to lower border of vertebra L1 in an adult. It is usually 1 cm lower than the celiac trunk. It initially travels in an anterior/inferior direction, passing behind/under the neck of the pancreas and the
splenic vein. Located under this portion of the superior mesenteric artery, between it and the aorta, are the following:
* left
renal vein
The renal veins are large-calibre veins that drain blood filtered by the kidneys into the inferior vena cava. There is one renal vein draining each kidney.
Because the inferior vena cava is on the right half of the body, the left renal vein is lo ...
- travels between the left
kidney
The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blood ...
and the
inferior vena cava
The inferior vena cava is a large vein that carries the deoxygenated blood from the lower and middle body into the right atrium of the heart. It is formed by the joining of the right and the left common iliac veins, usually at the level of the ...
(can be compressed between the SMA and the
abdominal aorta at this location, leading to
nutcracker syndrome
The nutcracker syndrome (NCS) results most commonly from the compression of the left renal vein (LRV) between the abdominal aorta (AA) and superior mesenteric artery (SMA), although other variants exist. The name derives from the fact that, in the ...
).
* the third part of the
duodenum, a segment of the
small intestines
The small intestine or small bowel is an organ in the gastrointestinal tract where most of the absorption of nutrients from food takes place. It lies between the stomach and large intestine, and receives bile and pancreatic juice through the pa ...
(can be compressed by the SMA at this location, leading to
superior mesenteric artery syndrome
Superior mesenteric artery (SMA) syndrome is a gastro-vascular disorder in which the third and final portion of the duodenum is compressed between the abdominal aorta (AA) and the overlying superior mesenteric artery. This rare, potentially life ...
).
*
uncinate process of pancreas
The uncinate process is a small part of the pancreas. The uncinate process is the formed prolongation of the angle of junction of the lower and left lateral borders in the head of the pancreas. The word "uncinate" comes from the Latin "uncinatus" ...
- this is a small part of the pancreas that hooks around the SMA.
The SMA typically runs to the left of the similarly named vein, the
superior mesenteric vein. After passing the neck of the pancreas it starts giving off its branches.
SMA branches
The number of arterial arcades in the ileum is more than the number of arcades in the jejunum.
The middle, right, and
ileocecal In many Animalia, including humans, an ileocolic structure or problem is something that concerns the region of the gastrointestinal tract from the ileum to the colon. In Animalia that have ceca, the ileocecal region is a subset of the ileocolic r ...
branches anastomose with each other to form a
marginal artery along the inner border of the colon. This artery is completed by branches of the left colic which is a branch of the
inferior mesenteric artery.
Clinical relevance
* Compared to other vessels of similar size, the SMA is largely spared from the effects of
atherosclerosis
Atherosclerosis is a pattern of the disease arteriosclerosis in which the wall of the artery develops abnormalities, called lesions. These lesions may lead to narrowing due to the buildup of atheroma, atheromatous plaque. At onset there are usu ...
. This may be due to protective haemodynamic conditions.
* Acute occlusion of the SMA almost invariably leads to
intestinal ischemia
Intestinal ischemia is a medical condition in which injury to the large or small intestine occurs due to not enough blood supply. It can come on suddenly, known as acute intestinal ischemia, or gradually, known as chronic intestinal ischemia. The ...
and often has devastating consequences, with up to 80% of SMA occlusions leading to death.
* The SMA can compress the left
renal vein
The renal veins are large-calibre veins that drain blood filtered by the kidneys into the inferior vena cava. There is one renal vein draining each kidney.
Because the inferior vena cava is on the right half of the body, the left renal vein is lo ...
, leading to
nutcracker syndrome
The nutcracker syndrome (NCS) results most commonly from the compression of the left renal vein (LRV) between the abdominal aorta (AA) and superior mesenteric artery (SMA), although other variants exist. The name derives from the fact that, in the ...
; and/or the third (horizontal) part of the
duodenum, leading to
superior mesenteric artery syndrome
Superior mesenteric artery (SMA) syndrome is a gastro-vascular disorder in which the third and final portion of the duodenum is compressed between the abdominal aorta (AA) and the overlying superior mesenteric artery. This rare, potentially life ...
.
Additional images
File:Volume rendered CT scan of abdominal and pelvic blood vessels (smaller).gif, Animated Volume rendered CT scan of abdominal and pelvic blood vessels.
File:Intestinal arteries.JPG, Superior mesenteric artery
File:Slide10gre.JPG, Dissection showing the anatomical relationship between the superior mesenteric artery and surrounding structures
References
External links
* - "Branches of the inferior mesenteric artery."
* - "Posterior Abdominal Wall: Branches of the Abdominal Aorta"
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* - "Posterior Abdominal Wall, Dissection, Anterior View"
*
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Arteries of the abdomen