islets of Langerhans

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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

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When implanted under the skin, the PEC-01 cells are designed to mature and further differentiate into insulin-producing beta and other endocrine cells that regulate blood glucose in a manner similar or identical to the islets that normally comprise the endocrine pancreas.
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Although the endocrine pancreas is not considered a classic estrogen target, estrogen effects on insulin and glucagon secretion and receptors of a classical and nonclassical nature are present in islet cells (Nadal et al.
The patients in the 2 reported cases of purely endocrine heterotopia presented clinically with melena and were found to have ulcerated gastric polypoid projections of ectopic endocrine pancreas.
In contrast to exocrine pancreatic adenocarcinoma, pancreatic islet cell tumors are rare, indolent tumors of the endocrine pancreas with an incidence of 5-10 per million worldwide annually.