Difference between revisions of "Duodenum" - New World Encyclopedia

From New World Encyclopedia
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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.
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The '''duodenum''' is first section of the [[small intestine]] in [[vertebrate]]s, including humans. In humans, it is shortest part of the small intestine, connecting the stomach to the jejunum, and it is where most chemical digestion takes place.
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==Overview=
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The vertebrate [[intestine]]—the long tube that extends from the stomach to the anus or cloaca— tends to be divided into a [[small intestine]] and a large intestine. The [[small intestine]] is the narrow tube of the [[gastrointestinal tract]] (gut) between the [[stomach]] and the [[large intestine]] that is responsible for most of the digestion. However, not all vertebrates have a stomach and a large intestine. For example, killifish (''Fundulus heteroclitus'') have a simple digestive system lacking both a large intestine and stomach, but do possess a small intestine (Vetter et al. 1985). [[Insectivore]]s lack a large intestine (Palaeos 2003).
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In [[human]]s and mammals, the small intestine is divided into three structural parts:
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* ''[[duodenum]]''.
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* ''[[jejunum]]''
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* ''[[ileum]]''
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The duodenum in humans is a hollow, jointed tube about 25-30 centimeters long, connecting the stomach to the [[jejunum]]. It begins with the [[duodenal bulb]] and ends at the [[ligament of Treitz]]. Food from the stomach is allowed into the duodenum by a [[muscle]] called the pylorus, or [[pyloric sphincter]], and is then pushed through the small intestine by a process of muscular-wavelike contractions called [[peristalsis]].
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The name ''duodenum'' is from the [[Latin]] ''duodenum digitorum'', twelve fingers' breadths.
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==Function==
 
==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 [[pH]] in the duodenum is approximately six. It also regulates the rate of emptying of the stomach via hormonal pathways.
 
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 [[pH]] in the duodenum is approximately six. It also regulates the rate of emptying of the stomach via hormonal pathways.
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==Notes==
 
==Notes==
 
<references/>
 
<references/>
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* Palaeos. 2003. [http://www.palaeos.com/Vertebrates/Units/460Insectivora/460.100.html Insectivora]. ''Palaeos''. Retrieved July 1, 2007.
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* Vetter, R. D., M. C. Carey, and J. S. Patton. 1985. Coassimilation of dietary fat and benzo(a)pyrene in the small intestine: An absorption model using the killifish. ''Journal of Lipid Research'' 26: 428-434.
  
 
==External links==
 
==External links==

Revision as of 00:44, 22 December 2007


Duodenum
BauchOrgane wn.png
Duodenum is #6
Illu small intestine.jpg
Small intestine
Gray's subject #248 1169
Artery Inferior pancreaticoduodenal artery, Superior pancreaticoduodenal artery
Vein Pancreaticoduodenal veins
Nerve celiac ganglia, vagus [1]
Precursor Foregut (1st and 2nd parts), Midgut (3rd and 4th part)
MeSH duodenum
Dorlands/Elsevier d_30/12315518

The duodenum is first section of the small intestine in vertebrates, including humans. In humans, it is shortest part of the small intestine, connecting the stomach to the jejunum, and it is where most chemical digestion takes place.

=Overview

The vertebrate intestine—the long tube that extends from the stomach to the anus or cloaca— tends to be divided into a small intestine and a large intestine. The small intestine is the narrow tube of the gastrointestinal tract (gut) between the stomach and the large intestine that is responsible for most of the digestion. However, not all vertebrates have a stomach and a large intestine. For example, killifish (Fundulus heteroclitus) have a simple digestive system lacking both a large intestine and stomach, but do possess a small intestine (Vetter et al. 1985). Insectivores lack a large intestine (Palaeos 2003).

In humans and mammals, the small intestine is divided into three structural parts:


The duodenum in humans is a hollow, jointed tube about 25-30 centimeters long, connecting the stomach to the jejunum. It begins with the duodenal bulb and ends at the ligament of Treitz. Food from the stomach is allowed into the duodenum by a muscle called the pylorus, or pyloric sphincter, and is then pushed through the small intestine by a process of muscular-wavelike contractions called peristalsis.

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 pH in the duodenum is approximately six. It also regulates the rate of emptying of the stomach via hormonal pathways.

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 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.

Additional images

Notes

  1. Physiology at MCG 6/6ch2/s6ch2_30 - Retrieved December 17, 2007.
  • Palaeos. 2003. Insectivora. Palaeos. Retrieved July 1, 2007.
  • Vetter, R. D., M. C. Carey, and J. S. Patton. 1985. Coassimilation of dietary fat and benzo(a)pyrene in the small intestine: An absorption model using the killifish. Journal of Lipid Research 26: 428-434.

External links

Digestive system - edit
Mouth | Pharynx | Esophagus | Stomach | Pancreas | Gallbladder | Liver | Small intestine (duodenum, jejunum, ileum) | Colon | Cecum | Rectum | Anus

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