The small intestine

In the small intestine, enzymes (substances produced by the body) break down nutrients such as carbohydrates, proteins or fats into their building blocks. These enzymes are produced in the salivary glands in the mouth, in the pancreas and in the intestinal cells. The intestinal cells absorb the building blocks (for example sugar, amino acids or fatty acids) together with vitamins, salts and water. From there, most of the nutrients enter the bloodstream to be carried to the rest of the body.

The small intestinal cells also produce various intestinal hormones. These hormones influence things like the production of bile or pancreatic juice. They also cause more water to be released into the intestine and make you feel full.

The large intestine

In the right lower abdomen, the small intestine leads into the large intestine, which is roughly 1 to 1.5 meters long. The large intestine is made up of the cecum, the appendix, the colon and the rectum, which ends at the anus in the anal canal. In the large intestine, strong, wave-like movements help to push the contents of the intestine towards the anus. The urge to go to the toilet and empty your bowels is triggered when stool enters the rectum. If we suppress this urge, the rectum temporarily stores the stool.

How often bowel movements occur varies greatly from person to person: It is completely normal to empty your bowel anywhere between three times a day to three times a week. The frequency mostly depends on how much fiber you get in your diet.

Another important task performed by the large intestine is the absorption of water and salts. There are also millions of bacteria in the large intestine. These bacteria break down proteins in the food to produce protein building blocks (amino acids). And they make the vital vitamins B and K.

Sources

• Menche N. (ed.) Biologie Anatomie Physiologie. Munich: Urban & Fischer/ Elsevier; 2012.
• Pschyrembel W. Klinisches Wörterbuch. Berlin: De Gruyter; 2014.
• Schmidt R, Lang F, Heckmann M. Physiologie des Menschen: mit Pathophysiologie. Heidelberg: Springer; 2011.

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