Acinus

For the acinus in the lung, see Lung § Respiratory zone.

An acinus (/ˈæsɪnəs/; pl.: 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.

Acinus
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
Identifiers
TH	H2.00.02.0.03050
Anatomical terminology [edit on Wikidata]

Exocrine glands

Acinar exocrine glands are found in many organs, including:

• the stomach^[1]
• the sebaceous gland of the scalp
• the salivary glands of the tongue^[2]
• the liver
• the lacrimal glands
• the mammary glands
• the pancreas^[3]
• the bulbourethral (Cowper's) glands

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.

Lungs

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 also

• Alveolar gland
• Intercalated duct