AskDefine | Define jejunum

Dictionary Definition

jejunum n : the part of the small intestine between the duodenum and the ileum

User Contributed Dictionary



  1. The central of the three divisions of the small intestine which lies between the duodenum and the ileum.


Extensive Definition

In anatomy of the digestive system, the jejunum is the central of the three divisions of the small intestine and lies between the duodenum and the ileum. The change from the duodenum to the jejunum is usually defined as the ligament of Treitz.
In adult humans, the small intestine is usually between 5.5-6m long, 2.5m of which is the jejunum.
The pH in the jejunum is usually between 7 and 8 (neutral or slightly alkaline).
The jejunum and the ileum are suspended by mesentery which gives the bowel great mobility within the abdomen. It also contains muscles to help move the food along.

Internal structure

The inner surface of the jejunum, its mucous membrane, is covered in projections called villi, which increase the surface area of tissue available to absorb nutrients from the gut contents. The epithelial cells which line these villi possess even larger numbers of microvilli. The transport of nutrients across epithelial cells through the jejunum and ileum includes the passive transport of sugar fructose and the active transport of amino acids, small peptides, vitamins, and most glucose. The villi in the jejunum are much longer than in the duodenum or ileum.
The jejunum contains very few Brunner's glands (found in the duodenum) or Peyer's patches (found in the ileum). Instead, it has many large circular folds in its submucosa called plicae circulares which increase the surface area for nutrient absorption.


Jejunum is derived from the adjective jejune, which means "fasting" or "hungry" in Early Modern English. It was so called because this portion of the intestine was found "empty" following death [Latin: jejunus, fasting; barren]

Additional images

Jejunum Image:Nudemousejejunum_EM.jpg|TEM of Mouse Jejunum x14000


External links

jejunum in German: Jejunum
jejunum in Spanish: Yeyuno
jejunum in Esperanto: Jejuno
jejunum in Persian: تهی‌روده
jejunum in French: Jéjunum
jejunum in Indonesian: Usus kosong
jejunum in Icelandic: ásgörn
jejunum in Italian: Digiuno (anatomia)
jejunum in Lithuanian: Tuščioji žarna
jejunum in Hungarian: Jejunum
jejunum in Dutch: Nuchtere darm
jejunum in Japanese: 空腸
jejunum in Polish: Jelito czcze
jejunum in Portuguese: Jejuno
jejunum in Slovak: Lačník
jejunum in Slovenian: Tešče črevo
jejunum in Turkish: Jejunum
jejunum in Chinese: 空腸
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