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 ?
Thousands of islet cells were painstakingly separated to ensure that only the highest quality, individual cells were analysed.
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Caught up in the frenzy over the supposed unlimited curative powers of embryonic stem cells, many have begun to argue that harvesting islet cells from cadavers is inefficient and unnecessary.
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The following journal articles illustrate the current worldwide experience with islet cell transplantation and the clinical outcomes achieved as well as the problems encountered with this treatment.