granula

Granula is a historical anatomical term meaning small grains. The word comes from Latin granulus, a diminutive of granum, and has been used to describe tiny granule-like structures observed in cells. In histology, granula often referred to cytoplasmic granules visible under light microscopy, particularly in neurons where Nissl granules or Nissl bodies describe the rough endoplasmic reticulum and ribosomes that stain basophilically. These granula reflect high ribosome content and are associated with protein synthesis.

Other prominent examples include zymogen granules in pancreatic acinar cells, where digestive enzyme precursors are stored prior to secretion, and various secretory granules found in endocrine and exocrine tissues. In a broader sense, granula can denote any small, granule-like inclusion within a cell, though modern terminology usually specifies the exact organelle or inclusion by name.

Today the term granula is largely historical and less common in contemporary texts, having been supplanted by precise terms for identifiable organelles and inclusions. When used, it often signals a general description of small intracellular bodies rather than a defined, standardized structure. In some older literature, the plural granula appears to refer to multiple tiny grains observed in tissue sections.

See also: granules, granulation tissue, Nissl body, zymogen granule.