120 THE ALIMENTARY SYSTEM. 



The Salivary Glands. 



The salivary glands are the parotid, sublingual, and submax- 

 illary, besides the numerous small mucous glands (labial, 

 buccal, lingual, and palatal) distributed over the mucous mem- 

 brane of the mouth and tongue. 



General structure : They are racemose glands, consisting of 

 saccules and ducts supported in sustentacular tissue, divided 

 into lobes and lobules, and well supplied with bloodvessels, 

 lymphatics, and nerves. 



The sustentacular connective tissue consists of a firm fibrous 

 capsule enveloping the entire gland, sending in trabeculse 

 (interlobular septa) which separate the various lobules and 

 bear the larger vessels and nerves and the interlobular ducts, 

 and of delicate intralobular tissue penetrating among the indi- 

 vidual saccules, and forming basement-membranes for their 

 support. 



The ultimate saccules or alveoli, the secreting portions of 

 the glands, are lined with polyhedral or spheroidal glandular 

 epithelial cells of the serous or mucous type. 



The interlobular ducts are lined with simple columnar 

 epithelium-cells, which toward their attached bases are marked 

 with longitudinal stria? or rods. 



In the intralobular and intermediate ducts the epithelium- 

 cells forming the lining become lower and more flattened. 



The salivary glands are amply supplied with bloodvessels, a 

 capillary plexus surrounding the various saccules. The lym- 

 phatics consist of lymph-spaces between the alveoli, and a 

 system of vessels. Fine terminal nerve-filaments are supplied 

 to the secretory-epithelium cells in great abundance, significant 

 of the well-known great pow r er which nervous influences 

 exert on the secretary action of these glands. 



The different salivary glands vary essentially only in the 

 character of their secretory elements. The parotid is a serous 

 gland, the sublingual is mucous, the submaxillary mixed. 



In the parotid gland the secreting epithelium and alveoli 

 are of the serous type. The saccules are lined with a single 

 layer of spheroidal, granular, deeply staining, opaque cells, 

 with rounded, central nuclei. In the resting stage, when 

 charged with secretion, the cells are more distended, encroach 



