The portions of cytoplasm that have many ribosomes stain in purple by a mixture of hematoxylin and eosin. It has already been mentioned that the affinity of acidic structures for basic dyes is called basophilia and these regions of the cytoplasm are basophilic.
A very demonstrative example of cytoplasmic basophilia can be seen in sections of the exocrine secretory cells of the pancreas, also called acinar cells of the pancreas. They produce a protein-rich secretion, the pancreatic juice.
The cells have a pyramidal shape or are pear-shaped. They are grouped in small spherical clusters called acini (singular: acinus). More details about these glands in the chapters “Glandular Epithelia” and “Pancreas”.
The center of the image shows one acinus, surrounded by parts of neighbor acini.
The cytoplasm of the base of each pyramidal acinar cell contains a large concentration of ribosomes that are rich in RNA and proteins. For this reason this area stains with both hematoxylin and eosin, resulting in a purple color.
As you move the mouse or click on the figure, two exocrine cells of an acinus will appear delimited.
The basophilic portion of their cytoplasm, at the basis of these cells, will appear in light blue. A few nuclei of acinar cells will appear shaded in a darker tone of blue. Nucleoli will appear as small dark-blue cilcles inside some nuclei.
The region at the opposite part of the cell basis, the “apical region” of each cell, is filled with secretory grains that contain high concentrations of proteins of the pancreatic juice. They are preferentially stained in pink-orange by acidic dyes such as eosin. This region is therefore acidophilic (or eosinohilic) and will become pink after you place the mouse or click on the image.
Pancreas. Hematoxylin and eosin. Medium magnification.
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