small intestine

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small intestine:

see intestineintestine,
muscular hoselike portion of the gastrointestinal tract extending from the lower end of the stomach (pylorus) to the anal opening. In humans this fairly narrow (about 1 in./2.
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Intestine, Small


the portion of the gut of vertebrate mammals, including man, that is situated between the stomach and the large intestine. The final digestion of food, the absorption of nutrients, and the movement of chyme occur in the small intestine.

In mammals, including man, the small intestine is divided into three sections: the duodenum, the jejunum, and the ileum. The length of the small intestine differs according to the nature of the digestive process: in man it is 6–7 m long, in cattle 27–49 m, in dogs 1.8–4.8 m, in cats 0.8–1.3 m, and in swine 16–21 m. In man the diameter of the small intestine is 48 mm in the initial section and 27 mm at the place where the ileum empties into the large intestine.

The walls of all sections of the small intestine are composed of mucous, submucous, and serous membranes and a muscular coat. Each section varies in the microscopic and submicroscopic characteristics of the intestinal wall, which reflect differences in function. The surface area of the small intestine’s mucous membrane is greatly increased by folds and protuberances: examples are the spiral valve in the mucous membrane of some fishes, and the villi, folds, and crypts in the small intestine of birds, mammals, and man.

Food is digested both in the intestinal cavity itself and by means of membrane-mediated (parietal) digestion. Cavitary digestion is achieved by the flow of pancreatic juice, bile, and intestinal juice into the lumen of the small intestine. During this process, supramolecular aggregates and the large molecules of proteins, carbohydrates, and fats in the food mass are hydrolyzed by the proteolytic, amylolytic, and lipolytic enzymes in the small intestine. The products of intermediate hydrolysis are adsorbed on the surface of the mucous membrane of the small intestine, where the final stages of hydrolysis and transition to absorption take place.

Parietal digestion is achieved by means of enzymes that are structurally bound to the cell membranes of the intestinal epithelium. The digestion and absorption of food in the small intestine are accompanied by contractions of the intestinal walls that mix and stir the chyme and propel it through the intestine.


small intestine

[′smȯl in′tes·tən]
The anterior portion of the intestine in humans and other mammals; it is divided into three parts, the duodenum, the jejunum, and the ileum.

small intestine

the longest part of the alimentary canal, consisting of the duodenum, jejunum, and ileum, in which digestion is completed
References in periodicals archive ?
For the secondary endpoint of changes in small bowel erosions, there was a significant difference between the misoprostol group and placebo group with a P value of .
All layers of small bowel were viable, and no inflammatory infiltrate was seen as shown in Figure 4a.
The present study also shows the effective role of MDCT enteroclysis in detection of small bowel diseases, both neoplastic and inflammatory.
ACG Clinical Guideline: Diagnosis and Management of Small Bowel Bleeding.
In the present case, we elected to perform urgent surgery, as the patient had identifiable small bowel masses and a transition point on imaging, along with no previous abdominal surgeries.
Since patients were sometimes referred from an outlying facility, previous results for studies that included upper endoscopy, colonoscopy, and small bowel follow through reports were unavailable to us via electronic medical record.
The polypoid pattern is the one most commonly found in small bowel metastasis [2, 10, 11] which is also true in our case and that may be the reason why the patient developed intussusception; the polypoid lesion acting as lead point.
3,7 Trichobezoars with small bowel extensions may produce other complications, namely bleeding, perforation, protein losing enteropathies, steatorrhoea, pancreatitis, appendicitis, and intussusceptions.
The small bowel video capsule is able to take photographs of the entire small bowel at a rate of 2 frames per second.
Associated findings, such as small bowel intussusception, mesenteric lymphadenopathy, and possible associated Celiac disease-related lymphoma, are also readily identifiable.
Ultrasonography (USG) and abdominal computed tomography (CT) have not been proven to be valuable in the early diagnosis of isolated small bowel injuries.
In the present case, dilated loops of small bowel indicated acute small bowel obstruction.