50 HISTOLOGY 







a remnant of secretion, are found near the orifice of the gland. Cells 

 such as have been described, which appear like cups filled with mucus, are 

 known as goblet cells. 



In certain stratified or pseudo-stratified epithelia, the formation of 

 mucus has been seen to take place in some of the deeper cells, but the dis- 

 charge of the secretion can occur only when these cells have reached the 

 free surface. 



THE NATURE AND CLASSIFICATION OF GLANDS. 



The simplest form of gland is merely a single secreting cell situated 

 apart by itself in an epithelium. Such unicellular glands are abundant 

 in invertebrates and are represented in man by scattered goblet cells. 

 In the higher animals the secreting cells usually occur in groups, and they 

 are generally found in tubular or saccular outpocketings of the epithelium. 



Excretory duct. 



Secretory duct. 



Intercalated duct 



End pieces. 



FIG. 47. DIAGRAM OF VARIOUS FORMS OF GLANDS. 

 The arrangement of ducts in D is that of the human submaxillary gland. 



An unbranched tubular gland is shown in vertical section in Fig. 46, and 

 in the diagram, Fig. 47, A. The secreting cells may be distributed through- 

 out the tube, or they may be limited to the lower part. In such cases 

 the upper part forms the duct of the gland. Sweat glands are unbranched 

 tubes, with a coiled secreting portion in the deeper part of the skin, 

 and a relatively long duct which conveys the secretion to the surface. 

 Many glands are branched, as in Fig. 47, B. The main stem becomes 

 the duct, and the characteristic secretion is formed in saccular or tubular 

 " end pieces." 



