Duodenum
70184
226181676
2008-07-17T05:24:21Z
Nmz787
6523175
{{Infobox Anatomy |
Name = Duodenum |
Latin = |
GraySubject = 248 |
GrayPage = 1169 |
Image = BauchOrgane wn.png |
Caption = Duodenum is #6 |
Image2 = Illu small intestine.jpg |
Caption2 = Small intestine |
Precursor = [[Foregut]] (1st and 2nd parts), [[Midgut]] (3rd and 4th part) |
System = |
Artery = [[Inferior pancreaticoduodenal artery]], [[Superior pancreaticoduodenal artery]] |
Vein = [[Pancreaticoduodenal veins]] |
Nerve = [[celiac ganglia]], [[vagus]] <ref>{{GeorgiaPhysiology|6/6ch2/s6ch2_30}}</ref> |
Lymph = |
MeshName = duodenum |
MeshNumber = A03.556.124.684.124 |
DorlandsPre = d_30 |
DorlandsSuf = 12315518 |
}}
{{Refimprove|date=June 2008}}
In [[anatomy]] of the [[digestive system]], the '''duodenum''' is a hollow jointed tube about 25-30 cm long connecting the [[stomach]] to the [[jejunum]]. It is the first and shortest part of the [[small intestine]] and it is where most chemical digestion takes place. It begins with the [[duodenal bulb]] and ends at the [[ligament of Treitz]]. The name ''duodenum'' is from the [[Latin]] ''duodenum digitorum'', twelve fingers' breadths.
==Function==
The duodenum is largely responsible for the breakdown of food in the small intestine. [[Brunner's glands]], which secrete [[mucus]], are found in the duodenum. The duodenum wall is composed of a very thin layer of cells that form the [[muscularis mucosae]]. The duodenum is almost entirely [[retroperitoneal]].
The duodenum also regulates the rate of emptying of the stomach via hormonal pathways. [[Secretin]] and [[cholecystokinin]] are released from cells in the duodenal epithelium in response to acidic and fatty stimuli present there when the pyloris opens and releases gastric chyme into the duodenum for further digestion. These cause the [[liver]] and [[gall bladder]] to release [[bile]], and the [[pancreas]] to release bicarbonate and digestive enzymes such as [[trypsin]], [[lipase]] and [[amylase]] into the duodenum as they are needed.
New studies have shown that around 80% of obese people who had [[gastric bypass surgery]] (bypassing the duodenum) were cured of their Type 2 Diabetes. However, the disappearance of their diabetes came long before the actual weight loss. When the same operation was performed on diabetic rats, they too were rid of their diabetes. However, when the operation was reversed in the animals, the diabetes returned. This shows that preventing food from entering the duodenum can have a dramatic impact on people suffering from Type 2 Diabetes.<ref name="60 Minutes - April 20, 2008">The Bypass Effect On Diabetes, Cancer</ref>
==Sections==
The duodenum is divided into four sections for the purposes of description. The first three sections form a "C" shape.
===First part===
The first (superior) part begins as a continuation of the duodenal end of the [[pylorus]]. From here it passes laterally (right), superiorly and posteriorly, for approximately 5 cm, before making a sharp curve inferiorly into the superior duodenal flexure (the end of the superior part). It is intraperitoneal.
===Second part===
The second (descending) part of the duodenum begins at the superior duodenal flexure. It passes inferiorly to the lower border of vertebral body L3, before making a sharp turn medially into the inferior duodenal flexure (the end of the descending part).
The [[pancreatic duct]] and [[common bile duct]] enter the descending duodenum, commonly known together as the [[hepatopancreatic duct]] (or [[pancreatic duct]] in the United States), through the major duodenal [[wiktionary:Papilla|papilla]]. This part of the duodenum also contains the minor duodenal papilla, the entrance for the [[accessory pancreatic duct]]. The junction between the embryological [[foregut]] and [[midgut]] lies just below the major duodenal papilla.
===Third part===
The third (inferior/horizontal) part of the duodenum begins at the inferior duodenal flexure and passes transversely to the left, crossing the [[inferior vena cava]], [[aorta]] and the [[vertebral column]].
===Fourth part===
The fourth (ascending) part passes superiorly, either anterior to, or to the right of, the aorta, until it reaches the inferior border of the body of the [[pancreas]]. Then, it curves anteriorly and terminates at the [[duodenojejunal flexure]] where it joins the [[jejunum]]. The duodenojejunal flexure is surrounded by a peritoneal fold containing muscle fibres: the [[ligament of Treitz]].
==Blood Supply==
The duodenum receives arterial blood from two different sources. The transition between these sources is important as it determines the foregut from the midgut. Proximal to the 2nd part of the duodenum (approximately at the major duodenal papilla - where the bile duct enters) the arterial supply is from the gastroduodenal artery and its branch the superior pancreatoduodenal artery. Distal to this point (the midgut) the arterial supply is from the superior mesenteric artery, and its branch the inferior pancreatoduodenal artery supplies the 3rd and 4th sections.
The superior and inferior pancreatoduodenal arteries (from the gastroduodenal artery and SMA respectively) form an anastomotic loop between the celiac trunk and the SMA; so there is potential for collateral circulation here.
The venous drainage of the duodenum follows the arteries. Ultimately these veins drain into the portal system, either directly or indirectly through the splenic or superior mesenteric vein.
==Lymphatic Drainage==
The lymphatic vessels follow the arteries in a retrograde fashion. The anterior lymphatic vessels drain into the pancreatoduodenal lymph nodes located along the superior and inferior pancreatoduodenal arteries and then into the pyloric lymph nodes (along the gastroduodenal artery).
The posterior lymphatic vessels pass posterior to the head of the pancreas and drain into the superior mesenteric lymph nodes. Efferent lymphatic vessels from the duodenal lymph nodes ultimately pass into the celiac lymph nodes.
==Additional images==
<gallery>
Image:Gray533.png|The celiac artery and its branches; the stomach has been raised and the peritoneum removed.
Image:Gray1041.png |Superior and inferior duodenal fossæ.
Image:Gray1042.png|Duodenojejunal fossa.
Image:Gray1050.png |Interior of the [[stomach]].
Image:Gray1058.png|Section of duodenum of cat. X 60.
Image:Gray1099.png|The pancreas and duodenum from behind.
Image:Gray1097.png|Transverse section through the middle of the first lumbar vertebra, showing the relations of the pancreas.
Image:Gray1100.png|The pancreatic duct.
Image:Small bowel duodenum with amyloid deposition congo red 10X.jpg|Duodenum with amyloid deposition in lamina propria.
Image:Illu pancrease.jpg|Region of pancreas
Image:Illu stomach2.jpg|Stomach
Image:Microvilli-Duodenum.JPG|Duodenum with brush border ([[microvilli|microvillus]])
</gallery>
==References==
<references/>
*60 Minutes [http://www.cbsnews.com/stories/2008/04/17/60minutes/main4023451.shtml "The Bypass Effect On Diabetes, Cancer"] April 20, 2008
==External links==
{{wiktionary}}
* {{NormanAnatomy|duodenum}}
{{digestive_system}}
[[Category:Digestive system]]
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[[zh:十二指肠]]