Gastrointestinal tract

Structure and Function of the Gastrointestinal Tract

  • The gastrointestinal tract extends from the mouth to the anus and includes organs such as the esophagus, stomach, and intestines.
  • The GI tract is divided into the upper and lower gastrointestinal tracts.
  • The upper tract consists of the mouth, pharynx, esophagus, stomach, and duodenum.
  • The lower tract includes most of the small intestine and all of the large intestine.
  • The small intestine is a tubular structure, usually between 6 and 7 meters long, and consists of three major divisions: duodenum, jejunum, and ileum.
  • The large intestine, also called the colon, starts at the cecum and ends at the rectum and anal canal.
  • The main function of the large intestine is to absorb water and salts.

Development and Layers of the Gastrointestinal Tract

  • The gut is an endoderm-derived structure that develops into the esophagus, stomach, and intestines.
  • The gut is patterned into three segments: foregut, midgut, and hindgut.
  • The gastrointestinal tract has four concentric layers: mucosa, submucosa, muscular layer, and adventitia or serosa.
  • The mucosa is highly specialized in each organ of the gastrointestinal tract and consists of epithelium, lamina propria, and muscularis mucosae.
  • The submucosa contains the submucosal plexus, an enteric nervous plexus.
  • The muscular layer consists of an inner circular layer and an outer longitudinal layer.
  • The myenteric plexus controls peristalsis and is located between the circular and longitudinal muscle layers.

Gene and Protein Expression in the Gastrointestinal Tract

  • Approximately 20,000 protein coding genes are expressed in human cells, with 75% of these genes expressed in at least one part of the digestive organ system.
  • Over 600 genes are specifically expressed in the gastrointestinal tract.
  • Proteins expressed in the stomach and duodenum have functions related to digestion and uptake of nutrients.
  • Specific proteins expressed in the stomach and duodenum are involved in defense against pathogens.

Transit Time and Immune Function of the Gastrointestinal Tract

  • The time taken for food to transit through the gastrointestinal tract varies.
  • Techniques such as radiography and breath hydrogen analysis can measure transit time.
  • The gastrointestinal tract forms an important part of the immune system, with various immune components and mechanisms in place to prevent pathogen invasion.
  • High fiber intake promotes a healthy immune system.

Clinical Significance of the Gastrointestinal Tract

  • Gastrointestinal diseases can affect the digestive system, including gastroenteritis, gastrointestinal cancer, and inflammatory conditions like ileitis and colitis.
  • Gastric infections, such as Helicobacter bacterium, can trigger inflammation known as gastritis.
  • Intestinal disorders like intestinal pseudo-obstruction and coeliac disease can impair intestinal function.
  • Other intestinal conditions include enteroviruses, endometriosis, bowel twist, angiodysplasia of the colon, and pseudomembranous colitis.
  • Animal intestines have various uses, such as obtaining rennet, sausage casings, and gut strings for musicians.

Gastrointestinal tract Data Sources

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