- One of the minute grape-shaped secretory portions of an acinous gland. Some authorities use the terms a. and alveolus interchangeably, whereas others differentiate them by the constricted openings of the a. into the excretory duct. [L. berry, grape]- liver a. a functional unit of the liver, comprising all of the liver parenchyma supplied by a terminal branch of the portal vein and hepatic artery; typically involves segments of two lobules lying between two terminal hepatic venules. SYN: Rappaport a..- pulmonary a. that part of the airway consisting of a respiratory bronchiole and all of its branches. SYN: primary pulmonary lobule, respiratory lobule.
* * *aci·nus 'as-ə-nəs, ə-'sī- n, pl aci·ni -.nī any of the small sacs or alveoli that terminate the ducts of some exocrine glands and are lined with secretory cells
* * *n. (pl. acini)1. a small sac or cavity surrounded by the secretory cells of a gland. Some authorities regard the term as synonymous with alveolus, but others distinguish an acinus by the possession of a narrow passage (lumen) leading from the sac.2. (in the lung) the tissue supplied with air by one terminal bronchiole. emphysema is classified by the part of the acinus involved (i.e. centriacinar, panacinar, or periacinar).• acinous adj.
* * *ac·i·nus (asґĭ-nəs) pl. aґcini [L. â€œgrapeâ€] a small saclike dilation, particularly in the lung or a gland. See also alveolus.
Medical dictionary. 2011.