CHAPTER XIII 

 GLANDS AND THE WORK OF EXCRETION 



IN our study so far we have been concerned mainly 

 with the introduction of materials into the body. We are 

 now to consider the removal of materials from the body. 

 The structures most directly concerned in this work are 

 known as 



Glands. As generally understood, glands are organs 

 that prepare special liquids in the body and pour them out 

 upon free surfaces. These liquids, known as secretions, 

 are used for protecting exposed parts, lubricating surfaces 

 that rub against each other, digesting food, and for other 

 purposes. They differ widely in properties as well as in 

 function, but are all alike in being composed chiefly of 

 water. The water, in addition to being necessary to the 

 work of particular fluids, serves in all cases as a carrier of 

 solid substances which are dissolved in it. 



General Structure of Glands. While the various glands 

 differ greatly in size, form, and purpose, they present strik- 

 ing similarities in structure. All glands contain the follow- 

 ing parts : 



r. Gland, or secreting, cells. These are specialized cells 

 for the work of secretion and are the active agents in 

 the work of the gland. They are usually cubical in shape. 



2. A basement membrane. This is a thin, connective 

 tissue support upon which the secreting cells rest. 



3. A network of capillary and lymph vessels. These 



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