The terms digestive tract or digestive canal ( Latin Canalis alimentarius ) are used to summarize the organs that are used to take in, chop up and transport food in order to digest it and make the nutrients it contains usable for the body. The digestive tract consists of the oral cavity , the pharynx (throat), the esophagus , the stomach and the intestines .
The largest part of the digestive tract is the gastrointestinal tract , which is also known as the gastrointestinal tract (from ancient Greek γαστήρ gastēr , German 'stomach' and Latin intestinum 'gut' ) or, less often, the gastrointestinal tract .
Other digestive organs are the liver with the biliary tract and the pancreas . All digestive organs together are called the digestive system (Latin: Apparatus digestorius ) or digestive system (Latin: Systema digestivum ).
In the digestive tract, the actual enzymatic digestion of food, the absorption of food and water and the elimination of indigestible or non-usable food components take place. In addition to enzymes, various microorganisms are also involved in digestion , which are summarized under the term intestinal flora .
The large digestive glands, the liver - with gall bladder - and the pancreas produce digestive juices that break down food into its components. The lower part of the digestive tract is mainly used for the absorption of water and the elimination of indigestible food components.
The digestive tract can be divided into a head and a torso (synonymous with the upper and lower digestive tract ). In addition to the actual gastrointestinal tract ( gastrointestinal tract ), the digestive system also includes the oral cavity , where mainly the mechanical grinding of food takes place, salivary glands, pharynx and the esophagus, which is used for further transport to the stomach. The assignment of the esophagus to the gastrointestinal tract is controversial.
The mouthparts and oral cavity ( lips , teeth , tongue ) are used for food intake and for crushing. The salivary glands produce saliva , which makes food slippery and in some mammals also contains enzymes to break down starch ( amylase ). The pharynx (pharynx, head) is the transition to the esophagus. In it, food and airways cross .
- Esophagus : is used to transport food from the mouth to the stomach.
- Stomach : pH = 2, converts the food into food pulp and enriches it with gastric juice . 15% of the proteins are split here by pepsin.
Small intestine with
- Duodenum ( duodenum ): The bile duct flows here, with him to the chyme pancreatic juice , which the protein - and fat digestion is used, and the bile that helps digest fat added.
- Jejunum ( jejunum ): Place the resorption of the now peptides split proteins ( dipeptides - / tripeptides ), the fats , carbohydrates , vitamins and water
- Ileum ( ileum )
- Large intestine (with caecum and appendix , ascending, and descending querverlaufendem colon ( Colon ) and rectum ): location of the feces in order to allow the feces at intervals, as well as the location of the absorption of water and electrolytes .
- After : used for excretion of the faeces.
Differentiation of the digestive systems
Through evolution, the digestive tract is optimally adapted to the respective food of the species . On the one hand it affects the anatomy of the digestive tract and on the other hand the environment of the nutrient-splitting microorganisms. Here is an overview of the common digestive systems:
- Simple system such as humans, pigs and dogs
Simple system with a functional appendix, such as in horses, rabbits and rats
- Small intestine
- Appendix (with microbial digestion)
- Large intestine
Multiple system ( ruminants ) such as cattle, sheep and goats
- Leaf stomach
- Abomasum (glandular stomach)
- Small intestine
- Appendix (pronounced but functionless)
- Large intestine
Avian system ( poultry ) such as chicken, turkey, duck
- Glandular stomach ( proventriculus or ventriculus glandularis )
- Gizzard ( Ventriculus muscularis ) (microbial digestion)
- Small intestine (main absorption site)
- Large intestine (microbial digestion)
- Cloaca (joint excretion of urine and feces)
The wall of the digestive tract basically consists of four tissues in all sections, which are in layers on top of each other. In the different sections of the gastrointestinal tract, the structure differs slightly depending on the function.
The layers from the inside out:
- Mucosa ( mucous membrane ): It forms the inner wall layer of the gastrointestinal tract.
- Submucosa : It forms a very narrow layer of connective tissue between the mucosa and the muscularis.
- Muscularis : In the mouth, pharynx and the upper part of the esophagus, this consists of striated muscles that are subject to voluntary action . B. can be tense when swallowing. In the remaining part of the digestive tract, the smooth muscles predominate, which are controlled by the parasympathetic nervous system. It is also responsible for the peristalsis of the intestine and is arranged both annularly and longitudinally so that the digestive tract can contract both longitudinally and transversely.
- Tunica serosa (also peritoneum viscerale ). Forms the outermost layer of tissue of the gastrointestinal tract. It secretes fluids and thus enables them to slide over one another with other organs. The serosa only occurs in organs that are located in the peritoneum. In the other areas of the body, the connection of individual organs is realized through loose connective tissue ( adventitia ).
There are a variety of diseases of the digestive tract from the oral cavity to the rectum and diseases of the digestive organs. For example, infections and inflammations such as inflammation of the oral mucosa, gastroenteritis , Crohn's disease and pancreatitis , but also certain intra-abdominal abscesses and various esophageal diseases and tumor diseases are included.
- Archenteron (creation of the primitive intestine and development to the digestive system in embryonic development)
- Inflammatory bowel disease
- Manfred Kirchgeßner: animal nutrition . 12th newly revised edition. DLG-Verlags-GmbH, Frankfurt am Main 2008, ISBN 978-3-7690-0703-9 , section “Differentiation of the digestive systems”.
- Franz-Viktor Salomon: digestive apparatus, apparatus digestorius . In: Franz-Viktor Salomon u. a. (Ed.): Anatomy for veterinary medicine . 2nd ext. Edition. Enke, Stuttgart 2008, ISBN 978-3-8304-1075-1 , pp. 235-323 .
- Pierre Hillemand: History of gastrointestinal medicine . In: Richard Toellner et al. (Ed.): Illustrated history of medicine . tape 4 . Andreas and Andreas, Salzburg 1986, p. 1784–1831 (French: Histoire de la médecine, de la pharmacie, de l'art dentaire et de l'art vétérinaire . Paris 1978. Special edition).
- Hans Adolf Kühn: Diseases of the digestive organs. In: Ludwig Heilmeyer (ed.): Textbook of internal medicine. Springer-Verlag, Berlin / Göttingen / Heidelberg 1955; 2nd edition ibid 1961, pp. 747-892.
- Internal endoscopy atlas with approx. 1000 images, videos and case studies
- Illustrated medical terminology of the digestive tract, University of Greifswald 2010 (PDF, 44 pages; 688 kB)