254 MUCOUS MEMBRANES GLANDS 



HISTOLOGIC TYPES OF GLANDS: 



1. Simple. 



2. Convoluted. 



I. Tubular J 



3. Branched. 



4. Compound. 



5. Compound tubulo-acinar (alveolar) ; racemose. 



1. Simple. 

 II. Saccular 



, J 2. Branched, 

 (alveolar) | , 



3. Compound. 



III. Ductless glands; endocrine glands. 



Glands of the tubular and saccular types contain an actively secreting 

 portion or fundus and a duct. Such externally secreting glands are also 

 known as 'exocrine' glands. In the ductless ('endocrine') glands the 

 duct is absent. The duct, though its epithelium may take some part 

 in the formation of the glandular secretion, primarily serves to convey 

 the secretion of the fundus to the free surface of the mucous membrane. 



The epithelium of the duct, as a rule, more or less closely resembles 

 that of the mucous membrane upon whose surface it opens. The epi- 

 thelium of the fundus, on the other hand, usually differs from that of 

 the duct and varies according to the nature of its secretion. In many of 

 the glands the epithelium is typically mucus secreting; others produce 

 a clearer, watery, and less viscid, serous secretion. Hence it is possible 

 to distinguish the following 



PHYSIOLOGIC TYPES OF GJ-ANDS I 



I. Serous glands. 



II. Mucous glands. 



III. Glands which are both mucous and serous (mixed glands). 



IV. Glands which are neither mucous nor serous. 



This physiologic classification is not in any way the equivalent of 

 the histologic gland types mentioned above. Thus both serous and 

 mucous glands, in different locations, form almost every variety of 

 tubular gland. 



DESCRIPTION OF PHYSIOLOGIC TYPES 



The glands of the fourth type arc too varied in their structure 

 to be considered collectively to advantage. The reader is referred to 



