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

References in periodicals archive ?
Kato, "The monocarboxylate transporters exist in the cattle endocrine pancreas," Histochemistry and Cell Biology, vol.
The current study proved a statistical significant affects on endocrine pancreas by showing an increase in area of islets of langerhans.
A nonclassical estrogen membrane receptor triggers rapid differential actions in the endocrine pancreas. Mol Endocrinol 16:497-505.
There are two kinds of diabetes mellitus, a disease of the endocrine pancreas. In type I diabetes, the body produces little or no insulin.
!n rainbow trout, for example, we have isolated three distinct mRNAs from the endocrine pancreas, each encoding a separate precursor: PPSS I, which contains a 14-amino acid sequence at its C-terminus (SS-14) that is highly conserved among vertebrates, as well as two others, PPSS II' and PPSS II", both containing [[Tyr.sup.7], [Gly.sup.10]]-SS-14 at their C-terminus (2).
Mutation of the multiple endocrine neoplasia type 1 gene in nonfamilial, malignant tumors of the endocrine pancreas. Cancer Res 1998;58:377-9.
Because of these two functions, the pancreas is referred to in two ways--the "exocrine pancreas" for the digestive tasks it performs and the "endocrine pancreas" for its role in producing hormones.
However, the inflammatory aspect of this disease also can damage islet cells and, therefore, the endocrine pancreas (Apte et al.
The endocrine pancreas is formed by pancreatic islets, also termed Langerhans islets, consisting of four different types of endocrine cells known as the beta, delta, alpha, and pancreatic polypeptide (PP) cells which produce, store, and release insulin, glucagon, somatostatin, and pancreatic peptide, respectively.
Metastatic lesions in the pancreas are very uncommon and may be difficult to differentiate from the more commonly encountered primary neoplasms derived from the exocrine and endocrine pancreas. Reported frequencies of intrapancreatic metastases vary considerably in the literature, from 4.5% in clinical series to 11% in autopsy series.
The exocrine pancreas consists of acinar and duct cells, the endocrine pancreas represents 2% of the pancreatic tissue and is organized into clusters of cells called islets of Langerhans.