duodenum

(noun)

The first part of the small intestine that starts at the lower end of the stomach and extending to the jejunum.

Related Terms

Examples of duodenum in the following topics:

  • Intestinal Phase

    • The duodenum initially enhances gastric secretion, but soon inhibits it.
    • Stretching of the duodenum accentuates vagal reflexes that stimulate the stomach, and peptides and amino acids in the chyme stimulate G cells of the duodenum to secrete more gastrin, which further stimulates the stomach.
    • Soon, however, the acid and semi-digested fats in the duodenum trigger the enterogastric reflex.
    • This gives the duodenum time to work on the chyme it has already received before being loaded with more.
    • The intestinal phase of digestion occurs in the duodenum, the first segment of the small intestine.

  • Anatomy of the Digestive System

    • The upper gastrointestinal tract consists of the esophagus, stomach, and duodenum.
    • Upon gross dissection, the duodenum may appear to be a unified organ, but it is often divided into two parts based upon function, arterial supply, or embryology.
    • Duodenum, the first section of the small intestine that may be the principal site for iron absorption.
    • Duodenum: Here the digestive juices from the pancreas (digestive enzymes) and the gallbladder (bile) mix together.
    • Jejunum: This is the midsection of the intestine, connecting the duodenum to the ileum.

  • Histology of the Small Intestine

    • The jejunum and ileum do not have Brunner's glands in the submucosa, while the ileum has Peyer's patches in the mucosa, but the duodenum and jejunum do not.
    • Brunner's glands (or duodenal glands) are compound tubular submucosal glands found in the duodenum.
    • The main function of these glands is to produce a mucus-rich, alkaline secretion (containing bicarbonate) in order to neutralize the acidic content of chyme that is introduced into the duodenum from the stomach, and to provide an alkaline condition for optimal intestinal enzyme activity, thus enabling absorption to take place and lubricate the intestinal walls.
    • They are aggregations of lymphoid tissue that are found in the lowest portion of the small intestine, which differentiate the ileum from the duodenum and jejunum.
    • This image shows the layers of the duodenum: the serosa, muscularis, submucosa, and mucosa.

  • Hormones of the Digestive System

    • Secretin is in the duodenum and signals the secretion of sodium bicarbonate in the pancreas and it stimulates the bile secretion in the liver.
    • Cholecystokinin (CCK) is in the duodenum and stimulates the release of digestive enzymes in the pancreas and stimulates the emptying of bile in the gall bladder.
    • Gastric inhibitory peptide (GIP) is in the duodenum and decreases the stomach churning in turn slowing the emptying in the stomach.
    • Motilin is in the duodenum and increases the migrating myoelectric complex component of gastrointestinal motility and stimulates the production of pepsin.

  • Anatomy of the Pancreas

    • Even when a single pancreas is present, two or three pancreatic ducts may persist, each draining separately into the duodenum (or an equivalent part of the foregut).
    • The superior pancreaticoduodenal artery from the gastroduodenal artery and the inferior pancreaticoduodenal artery from the superior mesenteric artery run in the groove between the pancreas and the duodenum and supply the head of pancreas.
    • 1: Head of pancreas 2: Uncinate process of pancreas 3: Pancreatic notch 4: Body of the pancreas 5: Anterior surface of the pancreas 6: Inferior surface of the pancreas 7: Superior margin of the pancreas 8: Anterior margin of the pancreas 9: Inferior margin of the pancreas 10: Omental tuber 11: Tail of the pancreas 12: Duodenum.

  • Associated Organs

    • The pancreas is located posterior to the stomach and next to the duodenum.
    • Pancreatic secretions accumulate in small ducts that drain to the main pancreatic duct, which drains directly into the duodenum.
    • The common bile duct and the pancreatic duct enter the duodenum together.
    • It is connected to the liver and the duodenum by biliary tree.
    • The gallbladder is connected to the main bile duct through the cystic duct, which in turn connects to the duodenum.

  • Absorption in the Small Intestine

    • Absorption of the majority of nutrients takes place in the jejunum, with the following notable exceptions: iron is absorbed in the duodenum; vitamin B12 and bile salts are absorbed in the terminal ileum; water and lipids are absorbed by passive diffusion throughout the small intestine; sodium bicarbonate is absorbed by active transport and glucose and amino acid co-transport; and fructose is absorbed by facilitated diffusion.

  • Other Hormone-Producing Structures

    • Secretin is in the duodenum and signals the secretion of sodium bicarbonate in the pancreas and it stimulates the secretion of bile in the liver.
    • Cholecystokinin (CCK) is in the duodenum and stimulates the release of digestive enzymes in the pancreas and stimulates the emptying of bile in the gall bladder.
    • Gastric inhibitory peptide (GIP) is in the duodenum and decreases the stomach churning, which in turn slows the emptying in the stomach.
    • Motilin is in the duodenum and increases the migrating myoelectric complex component of gastrointestinal motility and stimulates the production of pepsin.

  • Pancreas

    • The pancreas is located posterior to the stomach and next to the duodenum.
    • The exocrine function of the pancreas is controlled by the hormones gastrin, cholecystokinin, and secretin, which are hormones secreted by cells in the stomach and duodenum in response to food.
    • Pancreatic secretions accumulate in small ducts that drain to the main pancreatic duct that drains directly into the duodenum.
    • The pancreas is seen positioned with the duodenum slightly on top of it and next to the right kidney.

  • Pylorospasm and Pyloric Stenosis

    • There is narrowing (stenosis) of the opening from the stomach to the first part of the small intestine known as the duodenum, due to enlargement (hypertrophy) of the muscle surrounding this opening (the pylorus, meaning "gate"), which spasms when the stomach empties.
    • The gastric outlet obstruction due to the hypertrophic pylorus impairs emptying of gastric contents into the duodenum.
    • Once the stomach can empty into the duodenum, feeding can commence.