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Bowel

 

Ileus, Colon Cancer, Diverticulosis and Diverticulitis

 

The bowel consists of several very different sections: The short duodenum, which receives the chyme right from the stomach, the small bowel, a thin "hose" 4 - 5 m long, and the large bowel with a length of about 1.2 m. The many loops of the small bowel are relatively mobile in the abdominal cavity. They are supplied, contrary to the large bowel, by various blood vessels because it is here where many food components (glucose, proteins) are directly absorbed into the blood. The large bowel (colon) "frames" the loops of the small bowel and is divided into several sections.

 Darmkrankheiten

 

Where are the small and the large bowels located?

1. The first section of the large bowel is located in the right lower abdomen, where the small bowel empties into it, forming a several centimetres long piece of the bowel (caecum). It has a blind end, and from this end, there is a thin appendage, the appendix.

2. Above this section, the ascending part of the colon (colon ascendens) begins. It rises upwards almost as far as the liver and then curves (right flexure of the colon).

3. Above this section, the ascending part of the colon (colon ascendens) begins. It rises upwards almost as far as the liver and then bends (right flexure of the colon).

4. Then follows the section of the large bowel, which runs horizontally from the right to the left side in the upper abdomen (colon transversum, transverse colon). This part of the large bowel is kept in position by a fatty tissue in form of an apron and is coadunate with the colon. It is called colic omentum, "great net". Reaching the spleen in the left upper abdomen, the large bowel again bends (left flexure of the colon).

5. After this, the large bowel makes a double bend and is called colon sigmodeum, or just "sigma". Here, the large bowel ends and is followed by the last part, the rectum. The rectum is 16 cm long and passes into the anus.

In the middle of this "frame of the large bowel", there are several large blood vessels, which come centrally from the aorta and are embedded in a protective layer of tissue and continue in a radial form to the small bowel and the colon. It is very important for the surgeon to know exactly which vessel supplies which section of the bowel. This must be the basis to perform good colon surgery.

 

 

 

Functions of the small and the large bowel

The chyme partly digested in the stomach is mixed in the duodenum with bile juice and juices from the pancreas, splitting up the food into its components like sugar, fat, and protein. The good blood supply of the small bowel is responsible for the absorption of these components into the blood and for their processing in the body before the indigestible rest finally reaches the large bowel. It extracts the water from the still liquid chyme. But how does the bowel transport the chyme onwards and finally concentrate it? Even if a person has not eaten anything, periodical ripples run down the smooth musculature of the bowel from the gullet to the rectum and keep it continuously in motion, so that the chyme is transported onwards. In this process the loops of the small bowel "move" faster in comparison, so that the time, in which the chyme passes through, is quite short. Thus, this mechanism of a fast passage counteracts a highly increased quantity of bacteria, which naturally occur in the bowel. In the large bowel, the chyme takes longer to pass through, so that it can be thickened by the withdrawal of water. This is achieved by the motoricity of the colon, producing not only forward ripples of its loops, but also backward ones. At the same time, the quantity of bacteria in the colon rises drastically, which is completely normal and even desirable. The healthy colon has several mechanisms to bar off these bacteria and it produces certain proteins that have almost disinfecting abilities and are located on the mucous membrane of the colon. Diseases like intestinal obstruction (ileus) may considerably disturb this finely regulated system and cause grave consequences.

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