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.

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Normal histology of the breast, including an acinus in lower image. The terminal duct connected to the magnified acinus is not within this microsection.
Centroacinar cells.jpg
Centroacinar cells
Anatomical terminology

Exocrine glandsEdit

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

See alsoEdit


  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 S (2019). Principles of Pulmonary Medicine. Elsevier. p. 2. ISBN 978-0-323-52371-4.

External linksEdit