(C28-34) SLIDE 63: Pancreas, cat, (hematoxylin, methylene blue & basic fuchsin)

At medium magnifications the subdivision of the pancreas into lobules by thin connective tissue septa can clearly be seen (C28). Large interlobular ducts accompanied by numerous blood vessels can be seen in the heavier connective tissue beds serving several lobules. At higher magnification (C29) the acini are seen to be composed of strikingly polarized cells. The apex is filled with acidophilic secretory granules, while the base is filled with clumps of basophilic material (RER). In the center of favorably sectioned acini the nuclei of the centroacinar cells can be seen. The centroacinar cell and its associated acinus look somewhat like a flower, with the acinus representing the petals, and the centroacinar cell representing the pistil and stamen. The pale staining centroacinar cell marks the beginning of the intercalated duct. An intercalated duct with its simple squamous epithelium is shown in longitudinal section just to the right of center in C30. After leaving the acinus, intercalated ducts have simple squamous or simple cuboidal epithelium. Interlobular ducts have a definite connective sheath that distinguishes them from intralobular ducts. An interlobular duct with its simple cuboidal epithelium is present lying just beneath a metarteriole in C31. A larger interlobular duct is shown in C32. Note that the epithelium of the duct is tall simple columnar, and that the duct is surrounded by connective tissue in which small blood vessels can be identified.

Islets of Langerhans are present on this slide, but are difficult to distinguish from the acini. Look for clusters of reddish cells that lack the distinctive basophilia (blue) staining in their basal regions that is characteristic of the acini. In C33 there are two islets in the middle portion of the slide, separated by an isthmus of acinar cells. Can you spot them? Although there are A, B and D cells in these islets they are indistinguishable from one another because this stain does not differentiate between them. A consistent feature of the pancreas is the presence of large Pacinian corpuscles (C34), whose function is obscure.