Acinus, pulmonary: The ending of a tiny airway in the lung, where the alveoli (air sacs) are located.
In anatomy, an acinus is a round cluster of cells, usually epithelial cells, that looks somewhat like a knobby berry.
The word "acinus" means "berry" in Latin. (The plural is "acini".) There are also acini, round clusters of epithelial cells, in the salivary glands and in the pancreas.
Last Editorial Review: 5/13/2016