GLANDS 



221 



Duct Glands 



I. Tubular Glands. — (a) Simple tubular glands are simple 

 tubules which open on the surface, their lining epithelium being con- 

 tinuous with the surface epithelium. All the cells may be secreting 

 cells or only the more deeply situated. In the latter case the upper 

 portion of the tubule serves merely as a duct. In the more highly 

 developed of the simple tubular glands we distinguish a mouth, open- 

 ing upon the surface, a neck, usually somewhat constricted, and a 

 fundus, or deep secreting portion of the gland. 



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Fig. 132. — Diagram Illustrating Different Forms of Glands, i, simple tubular 

 gland; 2, coiled simple tubular gland; 3, branched simple tul)ular gland; 4, compound 

 tubular gland; la, 2a, and sa, simple alveolar glands; 4a, compound alveolar gland. 

 For description of la, 2a, and 3a, see simple alveolar glands in text. 



Simple tubular glands are divided according to the behavior of 

 the fundus, into (i) straight, (2) coiled, and (3) branched. 



(i) A straight tubular gland is one in which the entire tubule runs 

 a straight unbranched course, e.g., the glands of the large intestine 

 (Fig. 132, i). 



(2) A coiled tubular gland is one in which the deeper portion of 

 the tubule is coiled or convoluted, e.g., the sudoriferous glands of the 

 skin (Fig. 132, 2). 



(3) A forked or branched tubular gland is a simple tubular gland 

 in which the deeper portion of the tubule branches, the several 



