THE SALIVARY GLANDS 



385 



The lumen of the ducts is of considerable diameter and contains 

 the reticulated or granular particles of the secretion. The larger ducts 

 lie in the connective tissue septa which invest the lobular groups of 

 acini. Each of these groups is derived from the ramifications of the 

 terminal branch of an interlobular duct which enters the lobule to 

 divide into numerous intralobular ducts, and secondarily, through a 

 short intermediate or intercalary portion, into the 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 is more or less 

 tortuous and possesses a sacculated or alveo- 

 lar appearance. 



The epithelium differs accordingly as it 

 secretes a mucous or a serous fluid. Thus 

 the acini are either mucous or serous secret- 

 ing. 



THE SEROUS ACINI. The serous acini 

 contain pyramidal epithelial cells of sufficient 

 height to almost completely fill the tubule; 

 hence the lumen is very narrow. The form 

 of the secreting cells is somewhat irregular ' .intercalary duct; H; acini. 



Highly magnified (After 

 a tact which apparently depends upon their Flint.) 



crowded condition 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 gran- 

 ular, 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 flattened 

 'basket-cells' which here and there send short processes between the 

 cells of the secretory epithelium and thus provide cup-like depressions 

 which receive the bases of the secreting cells. The function and origin 

 of these 'basket-cells' is not at present known. They are readily recog- 

 nized by their deeply stained and flattened nuclei which are contained 

 within the thin cytoplasmic cell body. They may be immature acinal 

 cells, destined to replace worn-out secretory cells. 



The appearance of the secreting epithelium varies with its ae- 



FIG. 355. INTERCALARY 

 DUCTS AND ACINI OF 

 THE HUMAN SUBMAXIL- 

 LARY GLAND, CORROSION 

 MODEL. 



F, small intralobular duct, 



