- Basic concepts
- Functional esophageal disorders
- Functional gastroduodenal disorders
- General approach to gastroduodenal disorders
- Functional dyspepsia
- Belching disorders
- Nausea and vomiting disorders
- Functional bowel disorders
- Scientific update
- Resources
- Bibliography
Search
Basic concepts / Gastrointestinal Tract
Gastrointestinal Tract
"Whilst immunity mechanisms play a key role in the defense of the gut, a primary line of defense is provided by
- · the gut flora
- · the mucosal barrier
- · the gastrointestinal motility(3)"
Daily, the GI tract must face with the conflict between the need to absorb water and nutrients and the need to prevent bacteria, viruses, and other pathogens from entering the body. Thereby, the transporting epithelium of the GI tract is combined with an array of physiological defence mechanisms, including the microflora, mucus, digestive enzymes, acid, and the largest collection of lymphoid tissue existing in the body, that is, the gut-associated lymphoid tissue (GALT). " The intestinal mucosa contains 80% of the body's activated lymphocytes B" (3).
Microflora, the mucosal barrier, and the immune system are in charge of protecting the digestive system and the body from the threats coming from the outside world associated with daily nutrition. ]
The presence of beneficial microbes (commensals) in the intestine prevents colonization or overgrowth by potential pathogenic microbes, referred to as colonization resistance. Constant 'cross-talk' between the commensal microflora and the host epithelium triggers a wide array of host genes involved in intestinal maturation and mucosal barrier enhancement. This deliberate host-microbe cross-talk is reinforced by the colonization of the intestine by commensal bacteria, which bring unwanted microbes to bay. Furthermore, the presence of commensal microflora elicits anti-inflammatory systems action, which protects the intestinal epithelium from uncontrolled inflammation.
As many as 1014 bacteria (there are 10 times more bacteria than cells in the body), approximately 400 to 500 (even, scientists think this figure may reach more than 1,000) bacterial specie contained within the GI tract, with most of them being beneficial for the host health(2).
However, some gut bacteria are potentially pathogenic (e.g., Clostridium difficile, Clostridium perfringens, etc.). However, because they are present in a too small number and subject to competition with other saprophytic bacteria, their pathogenicity remains only latent.
While people tend to think about the digestive system primarily in terms of its digestive function, repelling foreign invaders is another challenge that our digestive system must face with.]
The GI tract is located in the interior of the body, but the lumen and its contents are part of the external environment. Therefore, the digestive system provides the largest surface for contact between the internal environment and the outside world, with its total surface area estimated to be equal to the size of a tennis court. The intestine uses a wide variety of defence systems to protect the host against aggressions from the external environment (i.e. pathogenic gut bacteria and viruses).
Author: Redaction
1. Macfarlane G.T., Macfarlane S. Human Colonic Microbiota: Ecology, Physiology and Metabolic Potential of Intestinal Bacteria. Scand J Gastroenterol 1997; 32 Suppl 222; 3-9.
2. Zoetendal EG, Vaughan EE, de Vos WM. A microbial World within us. Mol Microbiol 2006; 59(6): 1639-1650.
3. Cummings J.H. Antoine JM et al. "PASSCLAIM - Gut health and immunity", Eur J Nutr 2004; 43 Suppl 2: II118-II173.
1 - 2