SALIVARY GLANDS 



307 



secreting alveoli or acini. The intercalary ducts are lined by low 

 cuboidal epithelium and are the smallest tubules of the gland. 

 As the duct passes into the acinus the tubule is increased in size, 

 and its secretory epithelium becomes taller. The tubular acinus 

 k more or less tortuous and possesses a sacculated or alveolar 

 appearance. 



The epithelium differs accordingly as it secretes a mucous or a 

 serous fluid. Thus the acini are either mucous or serous secreting. 



The serous acini contain pyramidal epithelial cells of sufficient 

 height to almost completely fill the tubule; hence the lumen is 



^mpr 



FIG. 250. A GROUP OF SEROUS ACINI, FROM THE HUMAN SUBMAXILLARY GLAND. 

 a-a, interlobular connective tissue. Hematein and eosin. Photo, x 510. 



very narrow. The form of the secreting cells is somewhat irregu- 

 lar, a fact which apparently depends upon their crowded condi- 

 tion within the acinus. The nucleus is situated in the central 

 portion or in the proximal end of the cell and is spheroidal in 

 shape. The cytoplasm is finely granular, the granules being more 

 prominent in the distal portion of the cell. 



The epithelium rests upon a basement membrane within which, 

 beneath the bases of the secreting epithelial cells, are certain flat- 

 tened " "basket cells " which here and there send short processes be- 

 tween the cells of the secretory epithelium and thus provide cup- 



