Endocrine Pancreas

The endocrine pancreas is a diffuse organ that secretes hormones that regulate blood glucose levels

The islets of Langerhans, the endocrine component of the pancreas, are scattered throughout the organ in cell groupings of varying size (Fig. 17.22). The islets constitute about 1 to 2% of the volume of the pancreas but are most numerous in the tail. Individual islets may contain only a few cells or many hundreds of cells. Their polygonal cells are arranged in short, irregular cords that are profusely invested with a network of fenestrated capillaries. The definitive endocrine cells of the islets develop between 9 and 12 weeks of gestation.

In H&E-stained sections, the islets of Langerhans appear as clusters of pale-staining cells surrounded by more intensely staining pancreatic acini. It is not practical to attempt to identify the several cell types found in the islets in routinely prepared specimens (Fig. 17.23). After Zenker-formol fixation and staining by the Mallory-Azan method, however, it is possible to identify three principal cell types designated A (alpha), B (beta), and D (delta) cells (Table 17.2 and Fig. 17.24). With this method, the A cells stain red, the B cells stain brownish orange, and the D cells stain blue. About 5% of the cells appear to be unstained after this

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