Gastrointestinal Tract

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The digestive tract

digestion and absorption of nutrients

The main function of the digestive tract is the mechanical digestion (chewing), swallowing as well as the chemical digestion of food followed by absorption of nutrients and excretion of unnecessary substances. The primary organs of the digestive tract are mouth, pharynx, esophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine (colon), rectum and anal canal.

In addition, digestion is supported by auxiliary organs such as the salivary glands, liver, gall bladder and pancreas.

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Oral cavity, pharynx, esophagus

mechanical comminution and transport

Initially, the food is taken up through the oral cavity (cavum oris) and crushed by chewing. The crushed food pulp (bolus) is transported via the tongue into the middle section of the pharynx (oropharynx) and is then transported further by the partly reflexive act of swallowing. The bolus then passes through the lower part of the pharynx (hypopharynx) into the esophagus.

Stomach

storage and enzymatic breakdown

Once the bolus has arrived in the stomach (gaster), it is mixed, stored and further decomposed. The stomach is located intraperitoneal in the left upper abdomen and its external shape is very variable. The incoming food pulp is digested by gastric juice, which is produced by numerous glands in the gastric mucosa and has a high acid content (pH 1-1.5). Due to the high acidity, the stomach is able to render pathogens harmless and precipitate proteins. Furthermore, the gastric juice contains pepsinogen and lipase for further protein splitting and intrinsic factor for the absorption of vitamin B12.

Small and large Intestine

absorption of nutritions

Within the entire transport through the small intestine, enzymatic decomposition of food components and absorption of nutrients take place. The inner wall of the small intestine is greatly enlarged due to numerous indentations (crypts) and the raised folds of mucous membrane with villi and brush border on top. This strongly favors enzymatic decomposition and nutrient absorption. The large intestine, following the small intestine, thickens the initially liquid intestinal contents for storage and final excretion. Since the absorption of nutrients is already completed in this section of the digestive tract, only water and salts are reabsorbed. The unused components of the nutrition are excreted via the rectum and anal canal.

Diseases of the digestive tract

Common chronic inflammatory diseases of the digestive tract are ulcerative colitis and Crohn's disease. The marker calprotectin is of great importance for the detection and research of both diseases.

Colorectal cancer is also a common disease of the digestive tract and is an important research target with its tumor marker AFP (alpha fetoprotein) and CEA (carcinoembryonic antigen).

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