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The gastrointestinal tract is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and other animals, including the esophagus, stomach, and intestines. Food taken in through the mouth is digested to extract nutrients and absorb energy, and the waste expelled at the anus as faeces. Gastrointestinal is an adjective meaning of or pertaining to the stomach and intestines.
Peristalsis is a type of intestinal motility, characterized by radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an anterograde direction. Peristalsis is progression of coordinated contraction of involuntary circular muscles, which is preceded by a simultaneous contraction of the longitudinal muscle and relaxation of the circular muscle in the lining of the gut.
Constipation is a bowel dysfunction that makes bowel movements infrequent or hard to pass. The stool is often hard and dry. Other symptoms may include abdominal pain, bloating, and feeling as if one has not completely passed the bowel movement. Complications from constipation may include hemorrhoids, anal fissure or fecal impaction. The normal frequency of bowel movements in adults is between three per day and three per week. Babies often have three to four bowel movements per day while young children typically have two to three per day.
Laxatives, purgatives, or aperients are substances that loosen stools and increase bowel movements. They are used to treat and prevent constipation.
The enteric nervous system (ENS) or intrinsic nervous system is one of the three main divisions of the autonomic nervous system (ANS), the other being the sympathetic (SNS) and parasympathetic nervous system (PSNS), and consists of a mesh-like system of neurons that governs the function of the gastrointestinal tract. It is capable of acting independently of the SNS and PSNS, although it may be influenced by them. The ENS is nicknamed the "second brain". It is derived from neural crest cells.
Hirschsprung's disease is a birth defect in which nerves are missing from parts of the intestine. The most prominent symptom is constipation. Other symptoms may include vomiting, abdominal pain, diarrhea and slow growth. Most children develop signs and symptoms shortly after birth. However, others may be diagnosed later in infancy or early childhood. About half of all children with Hirschsprung's disease are diagnosed in the first year of life. Complications may include enterocolitis, megacolon, bowel obstruction and intestinal perforation.
Diverticulosis is the condition of having multiple pouches (diverticula) in the colon that are not inflamed. These are outpockets of the colonic mucosa and submucosa through weaknesses of muscle layers in the colon wall. Diverticula do not cause symptoms in most people. Diverticular disease occurs when diverticula become clinically inflamed, a condition known as diverticulitis.
The myenteric plexus provides motor innervation to both layers of the muscular layer of the gut, having both parasympathetic and sympathetic input, whereas the submucous plexus provides secretomotor innervation to the mucosa nearest the lumen of the gut.
Functional gastrointestinal disorders (FGID), also known as disorders of gut–brain interaction, include a number of separate idiopathic disorders which affect different parts of the gastrointestinal tract and involve visceral hypersensitivity and motility disturbances.
Gastrointestinal diseases refer to diseases involving the gastrointestinal tract, namely the esophagus, stomach, small intestine, large intestine and rectum; and the accessory organs of digestion, the liver, gallbladder, and pancreas.
Toxic megacolon is an acute form of colonic distension. It is characterized by a very dilated colon (megacolon), accompanied by abdominal distension (bloating), and sometimes fever, abdominal pain, or shock.
A fecal impaction or an impacted bowel is a solid, immobile bulk of feces that can develop in the rectum as a result of chronic constipation. Fecal impaction is a common result of neurogenic bowel dysfunction and causes immense discomfort and pain. Its treatment includes laxatives, enemas, and pulsed irrigation evacuation (PIE) as well as digital removal. It is not a condition that resolves without direct treatment.
Intestinal neuronal dysplasia (IND) is an inherited disease of the intestine that affects one in 3000 children and adults. The intestine uses peristalsis to push its contents toward the anus; people with IND have a problem with the motor neurons that lead to the intestine, inhibiting this process and thus preventing digestion.
Megacolon is an abnormal dilation of the colon. This leads to hypertrophy of the colon. The dilation is often accompanied by a paralysis of the peristaltic movements of the bowel. In more extreme cases, the feces consolidate into hard masses inside the colon, called fecalomas, which can require surgery to be removed.
Gut-associated lymphoid tissue (GALT) is a component of the mucosa-associated lymphoid tissue (MALT) which works in the immune system to protect the body from invasion in the gut.
Intestinal pseudo-obstruction (IPO) is a clinical syndrome caused by severe impairment in the ability of the intestines to push food through. It is characterized by the signs and symptoms of intestinal obstruction without any lesion in the intestinal lumen. Clinical features mimic those seen with mechanical intestinal obstructions and can include abdominal pain, nausea, abdominal distension, vomiting, dysphagia and constipation depending upon the part of the gastrointestinal tract involved.
Harald Hirschsprung was a Danish physician who first described Hirschsprung's disease in 1886.
The gastrocolic reflex or gastrocolic response is a physiological reflex that controls the motility, or peristalsis, of the gastrointestinal tract following a meal. It involves an increase in motility of the colon consisting primarily of giant migrating contractions, in response to stretch in the stomach following ingestion and byproducts of digestion entering the small intestine. The reflex propels existing intestinal contents through the digestive system helps make way for ingested food, and is responsible for the urge to defecate following a meal.
The detrusor muscle, also detrusor urinae muscle, muscularis propria of the urinary bladder and muscularis propria, is smooth muscle found in the wall of the bladder. The detrusor muscle remains relaxed to allow the bladder to store urine, and contracts during urination to release urine. Related are the urethral sphincter muscles which envelop the urethra to control the flow of urine when they contract.
The gastrointestinal wall of the gastrointestinal tract is made up of four layers of specialised tissue. From the inner cavity of the gut outwards, these are the mucosa, the submucosa, the muscular layer and the serosa or adventitia.
References
- ↑ Holschneider, A.M.; Puri, P., eds. (2008). Hirschsprung's disease and allied disorders. Springer. doi:10.1007/978-3-540-33935-9. ISBN 978-3-540-33935-9.
- 1 2 Meier-Ruge WA, Bruder E (2005). "Pathology of chronic constipation in pediatric and adult coloproctology". Pathobiology. 72 (1–2): 1–102. doi:10.1159/000082310. PMID 15902901.
- ↑ Meier-Ruge WA (October 1998). "Desmosis of the colon: a working hypothesis of primary chronic constipation". Eur J Pediatr Surg. 8 (5): 299–303. doi:10.1055/s-2008-1071218. PMID 9825241.
- ↑ Feichter, Sonja; Meier-Ruge, William A.; Bruder, Elisabeth (2009-11-01). "The histopathology of gastrointestinal motility disorders in children". Seminars in Pediatric Surgery. Gastrointestinal Motility Disorders. 18 (4): 206–211. doi:10.1053/j.sempedsurg.2009.07.002. ISSN 1055-8586.
- 1 2 Meier-Ruge WA, Bruder E (March 2007). "[The morphological characteristics of aplastic and atrophic desmosis of the intestine]". Pathologe (in German). 28 (2): 149–54. doi:10.1007/s00292-007-0896-8. PMID 17279408.
- ↑ Meier-Ruge & Bruder 2005 , pp. 78–81, §Atrophic desmosis as secondary connective tissue atrophy in muscularis propria
- ↑ Martucciello G (June 2008). "Hirschsprung's disease, one of the most difficult diagnoses in pediatric surgery: a review of the problems from clinical practice to the bench". Eur J Pediatr Surg. 18 (3): 140–9. doi:10.1055/s-2008-1038625. PMID 18493886.