islets of Langerhans


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Related to islets of Langerhans: insulin, pancreas, somatostatin

islets of Langerhans:

see pancreaspancreas
, glandular organ that secretes digestive enzymes and hormones. In humans, the pancreas is a yellowish organ about 7 in. (17.8 cm) long and 1.5 in. (3.8 cm) wide. It lies beneath the stomach and is connected to the small intestine at the duodenum (see digestive system).
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Islets of Langerhans

 

the groups of cells in the pancreas of man and vertebrates (except cyclostomes) that form the endocrine part of the organ, secreting the hormones insulin and glucagon into the blood.

The islets of Langerhans are named for the German scientist P. Langerhans, who described them in 1869. In 1901, the Russian scientist L. V. Sobolev proved their endocrine function and established the occurrence of changes in the islets with diabetes mellitus. The dimensions of the islets of Langerhans are 50 to 500 microns, and there are between ten and 20 islets per mg of gland tissue. The islets do not communicate with the gland’s effluent ducts.

The islets of Langerhans develop from tubular processes of the anterior gut and, depending on the type of animal, consist of cells of several types. All animals have α cells and β cells. The granules of α cells are considered to be a form of glucagon deposit; the β cells, of insulin. C cells and D cells (the former have been found in the islets of Langerhans of guinea pigs; the latter, in man and dogs), which lack granules, are converted to α cells and β cells. In all, the tissue of the islets of Langerhans makes up 0.9 to 3.6 percent of the mass of the pancreas in children and 0.9 to 2.7 percent in adults.

V. M. SAMSONOVA

References in periodicals archive ?
Actual distribution of the number and volume of the islets of Langerhans in different size classes in non-diabetic humans of varying ages.
A historical perspective on the identification of cell types in pancreatic islets of Langerhans by staining and histochemical techniques.
Caption: Figure 1: The tissue sections of control pancreas (H&E; (a) x100; (b) x400) show islets of Langerhans (a) and intact islet cells (b) and acinar cells with no remarkable alterations.
The small clusters of endocrine cells forming the islets of langerhans were present in the parenchyma of the gland.
In both control groups (C and CA), islets of Langerhans were present with normal size and shape.
In 1910, Sir Edward Albert Sharpey-Schafer suggested that people with diabetes were deficient in a single chemical that was normally produced by the pancreas -- he proposed calling this substance ''insulin"', from the Latin ''insula'', meaning island, in reference to the insulinproducing islets of Langerhans in the pancreas.
The Islets of Langerhans try to adapt themselves to this condition by increasing the number of insulin-producing beta-cells and/or modulating their individual secretion of insulin in response to the intake of sugar.
History has shown us that student research can have big impact for the entire scientific community; the discovery of Islets of Langerhans as well as Insulin are some of the groundbreaking discoveries contributed by medical students (1).
Unniappan's findings indicate that the protein stimulates insulin secretion from the pancreas, a glandular organ, which contains clusters of cells called the islets of Langerhans. These islets produce several important hormones, including the primary glucose-lowering hormone, insulin.
During alloxan treatment, [beta]-cytotoxin causes a massive destruction of [beta]-cells in islets of Langerhans, and reduces the [beta]-cells and insulin release (Colca et al., 1983).
The islets of Langerhans from male offspring presented altered [Ca.sup.2+] signaling and insulin secretion.
In a 1982 study, insulin secretion from islets of Langerhans exposed to low-frequency pulsed magnetic fields decreased compared with controls (p < 0.002) (Bioelectromagnetics 4[1]:103-106).