282 



THE ORGANS 



and mucous (page 226). Only the general structure of these glands is 

 here described, the minute structure of mucous and serous glands 

 having been described on page 226. 



Each gland consists of gland tissue proper and of a supporting 

 connective-tissue framework. The framework consists of a connect- 

 ive-tissue capsule which encloses the gland, but blends externally 

 with and attaches the gland to the surrounding structures. From 

 the capsule traheculcB pass into the gland, subdividing it into lohes 

 and lobules. The gland tissue proper consists of systems of excretory 

 ducts opening into secretory tubules, all being lined with one or more 

 layers of epithelial cells. Each gland has one mam excretory duct. 

 This divides into branches — interlobar ducts — which run to the lobes 

 in the connective tissue which separates them. The interlobar ducts 



give rise to branches which, as they pass to 

 the lobules in the interlobular connective 

 tissue, are known as interlobular ducts. From 

 the latter, branches enter the lobules — intra- 

 lobular ducts — and split up into terminal 

 secreting tubules which constitute the bulk 

 of the lobule. As the smaller intralobular 

 ducts are lined with cells of a secretory type, 

 and probably take part in the elaboration 

 of the secretion of the gland, they have 

 been called salivary or secreting tubules. 

 These, in the submaxillary and parotid 

 glands, open into tubules which have a nar- 

 row lumen and are lined with low or flat 

 epithelium; lying between the secreting 

 tubules and the terminal tubules, they are 

 known as intercalated or intermediate tubules. 

 From the interlobular connective tissue 

 delicate extensions pass into the lobules, 

 separating the gland tubules. The glandular 

 tissue is known as the parenchyma of the gland in contradistinction 

 to the connective or ititerstitial tissue. 



The parotid gland in man, dog, cat, and rabbit is a purely serous 

 gland. Its duct system is complex. The main excretory duct 

 (Stenoni) is lined with two layers of columnar epithelium resting upon a 

 distinct basement membrane. The main duct divides into numerous 

 branches, which in turn give rise to the secreting or salivary tubules. 



Fig. 183. — Reconstructed 

 Model of Small Muco-serous 

 Gland. Dotted parts corre- 

 sponding to the ' ' 

 (Maziarski). 



crescents 



