Duodenum

The duodenum is part of the digestive system.

Function of the duodenum

The duodenum is the first part of the small intestine (the next two parts are the jejunum and ileum). The duodenum is located after the stomach in the digestive system (via the pylorus). Its purpose is to neutralise the strong acidity of chyme (food digested by the stomach).

Structure of the duodenum

The duodenum is approximately 4 centimetres in diameter and 25 to 30 centimetres long. It takes its name from the Latin that means "twelve fingers" because of the length of the organ (which is approximately equivalent to the width of twelve fingers). It can be divided into four segments (D1 to D4) which are separated by angles.

The four layers of the wall of the duodenum from inside towards the outside are:

• the mucosa which has folds and Brünner glands (which secrete the alkaline mucoid that neutralises the acidity);
• the submucosa which is supplied with vessels and nerves;
• the longitudinal and circular smooth muscles;
• and the peritoneum (or serosal membrane).