Duodenum Function

Duodenum is a short tube like organ, which is usually considered as the first segment of the small intestine. The other two parts of the small intestine are jejunum and ileum. In humans, duodenum is about 25 to 30 cm in length, and it connects the stomach and the jejunum. As one of the most important parts of the digestive system, it is concerned with both digestion of foods and absorption of nutrients. In fact, it is the major site for iron absorption. Several ducts from pancreas, liver and gallbladder open into the duodenum to facilitate its main functions.

It is located just below the stomach, and its first part is quite close to the liver and the pancreas. It is located between the stomach and the jejunum. Anatomically, this small organ is divided into four parts or segments, which are known as the superior, descending, horizontal and ascending duodenum. It is a C-shaped organ, inner lining of which is made of crypts. These crypts are responsible for increasing the surface area of the intestinal membrane and thereby ensure better digestion. It also contains smooth muscles, which help it to move the waste materials down to the large intestine. In addition to these, it receives several ducts coming from the pancreas, gallbladder and liver.

The Role of Duodenum

Its main function is to receive the partially digested foods from the stomach, and complete the process of digestion. In the stomach, foods are mixed with stomach acids and digested partially. This mixture of semi digested foods and stomach acids is known as chyme. It receives this chyme from the stomach, and then starts the breakdown foods with the help of enzymes and intestinal juice. It also receives bile from the liver and the gallbladder, and pancreatic juice from the pancreas. These secretions are of immense importance for ensuring the proper digestion of foods in the duodenum.

Along with digesting foods, it is responsible for regulating the rate of gastric emptying, as well as triggering the hunger signals. Gastric emptying refers to the emptying of the stomach, i.e. the process of food leaving the stomach and entering the duodenum. These functions are facilitated by the hormones secreted from the duodenal epithelium. There is a small circular opening between the stomach and the duodenum, known as pylorus, which releases the chyme into the duodenum. The cells present in the epithelium of duodenum in turn, release two hormones known as secretin and cholecystokinin. Secretin is released in response to too much acid in the small intestine or duodenum, while secretion of cholecystokinin is stimulated by the presence of amino acids and fatty acids. These two hormones stimulate the liver and the gallbladder to release bile, as well as the pancreas to secrete enzymes (lipase, amylase and trypsin) into the duodenum.

After the completion of digestion, it absorbs the nutrients, from where the nutrients enter the bloodstream. To sum up, its main functions in the digestive system are, digestion of foods, absorption of nutrients, controlling the rate of gastric emptying, and regulating hunger and the movement of food throughout the gastrointestinal tract. It has been found that more foods and nutrients are absorbed in duodenum than stomach. Gastric bypass surgery often involves the duodenum, due to its immense importance in the absorption of nutrients, and regulation of hunger and movement of food. In gastric bypass surgery, usually the duodenum is bypassed in an attempt to lower the absorption of nutrients and calories.