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.

IA. L. KARAGANOV

small intestine

[′smȯl in′tes·tən]
(anatomy)
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 ?
Three-dimensional structure of the human small intestinal mucosa in health and disease.
Influence of dietary glutamine supplementation on growth performance, small intestinal morphology, immune response and some blood parameters of broiler chickens.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5] show small intestinal stromal tumor, lymphoma, angioma, duplication, and leiomyosarcoma.{Table 1}{Figure 1}{Figure 2}{Figure 3}{Figure 4}{Figure 5}
It is concluded that compared to individual supplementation mannanoligosaccharide (MOS) and organic acid blend (OAB) in combination increased carcass weight, carcass yield and small intestinal microarchitecture in broilers.
Intraepithelial lymphocytosis in architecturally preserved proximal small intestinal mucosa: An increasing diagnostic problem with a wide differential diagnosis.
Examination of H&E stained small intestinal sections of each of controls, DFO, and Quercetin groups showed the same normal histological architecture of small intestine that comprises 4 distinct layers; the mucosa, submucosa, muscularis externa, and serosa.
Ghoshal, "Small intestinal bacterial overgrowth and other intestinal disorders," Gastroenterology Clinics of North America, vol.
The small intestinal transit time was the time of the capsule entering the cecum minus the time of it entering the duodenum.
Aziyo's biologic extracellular matrix for vascular repair is constructed from a multi-laminate sheet of decellularized, non-crosslinked, lyophilized extracellular matrix (ECM) derived from pig small intestinal submucosa (SIS).
For the study, the researchers exposed a small intestinal cell culture model to the physiological equivalent of a meal's worth of titanium oxide nanoparticles - 30 nanometers across - over four hours (acute exposure), or three meal's worth over five days.

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