Synonyms in a broader sense
Interstitium tenue, jejunum, ileum, duodenum
Definition
The small intestine is the section of the digestive tract that follows the stomach. It is divided into three sections. It begins with the duodenum, followed by the jejunum and ileum.
The main function of the small intestine is to split the food pulp (chyme) into its smallest components and to absorb these components through the intestinal mucosa. This section directly follows the stomach outlet (pylorus). It is approx.
24 cm long, has the shape of a “C ́s” and encloses with this “C” the head of the pancreas. The duodenum is additionally divided into an upper part (pars superior), which directly adjoins the pylorus, the descending part (pars descent), the horizontal part (pars horizontalis) and the ascending part (pars ascendens). The duodenum is the only part of the small intestine which is firmly attached to the rear wall of the abdomen.
In its descending part, the excretory ducts of the bile duct (Ductus choledochus) and the pancreatic duct (Ductus pancreaticus) end. These usually end together in the papilla vateri (major duodenal papilla). If, in rare cases, the ducts open separately into the duodenum, there is an additional pancreatic outlet into a smaller papilla (minor duodenal papilla).
- Thyroid cartilage larynx
- Trachea (windpipe)
- Heart (Cor)
- Stomach (Gaster)
- Large intestine (colon)
- Rectum (rectum)
- Small intestine (ilium, jejunum)
- Liver (Hepar)
- Lung, or lung wing
Empty gut crumpled gut
The two longer parts of the small intestine – jejunum and ileum – are located in the middle of the abdominal cavity and are framed by the large intestine. These two sections of the small intestine are very mobile because they are suspended on a special suspension structure called the mesentery, which flexibly attaches the intestine to the posterior abdominal wall. This fat-rich structure also contains the blood vessels, nerves and lymph nodes that supply the small intestine.
The small intestine is suspended from the mesentery in such a way that it lies in large folds, also known as the small intestinal crest. The empty intestine (jejunum) is about 3.5 m long, the ileum measures about 2.5 m. Between these two sections of the small intestine, no sharp border can be seen with the naked eye. Only histologically, the small intestine parts can be distinguished from each other.
At the end of the small intestine, the ileum opens laterally into the appendix part of the large intestine, this opening being covered by the large intestinal valve (ileozaecal valve, Bauhin’s valve). This valve serves as a functional closure of the ileum in relation to the colon. Through this valve, the bacteria that have colonized the colon cannot enter the sterile small intestine.
All articles in this series:
