Normal histology of the breast, including an acinus in lower image. The terminal duct connected to the magnified acinus is not within this microsection.
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.
Exocrine glands
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.
