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Illustrated section of pancreas of dog. X 250. (Alveolus labeled at center top.)
Centroacinar cells.jpg
Centroacinar cells
Anatomical terminology
human acinar cells

An acinus (/ˈæsɪnəs/; plural, acini; adjective, acinar /ˈæsɪnər/ or acinous) refers to any cluster of cells that resembles a many-lobed "berry," such as a raspberry (acinus is Latin for "berry"). The berry-shaped termination of an exocrine gland, where the secretion is produced, is acinar in form, as is the alveolar sac containing multiple alveoli in the lungs.

Exocrine glands[edit]

Acinar exocrine glands are found in many organs, including:

The thyroid follicles can also be considered of acinar formation but in this case the follicles, being part of an endocrine gland, act as a hormonal deposit rather than to facilitate secretion.
Mucous acini usually stain pale, while serous acini usually stain dark.
The term "acinus" is considered synonymous with alveolus by some sources, but not all.


The end of the respiratory bronchioles in the lungs mark the beginning of a pulmonary acinus that includes the alveolar ducts, alveolar sacs, and alveoli.[4]

See also[edit]


  1. ^ Histology image: 51_07 at the University of Oklahoma Health Sciences Center - pyloric stomach
  2. ^ Histology image: 46_03 at the University of Oklahoma Health Sciences Center - sublingual gland
  3. ^ Histology image:10405loa from Vaughan, Deborah (2002). A Learning System in Histology: CD-ROM and Guide. Oxford University Press. ISBN 978-0195151732.
  4. ^ Weinberger, Steven (2019). Principles of Pulmonary Medicine. Elsevier. p. 2. ISBN 9780323523714.

External links[edit]