PROGRESSIVK TISSUE CHANGES. 



191 



HYPERl'LASIA. 

 DEFINITION. 

 VARIETIES. 



Piireiu-liyinatous. 



Interstitial 

 ETIOLOGY. 

 APPEARANCE. 



Macroscopic. 



Microscopic. 

 TISSUE AFFECTED. 

 EFFECTS. 



flyperplasia. according to the derivation of the word, is ex- 

 cessive formation. Hvperplasia and hypertrophy are incorrectly 

 used interchangeably by some. Hyperplasia should be used to 

 designate the condition resulting from an abnormal increased 

 size of a part due to an increase in the number of cells of the 

 part. Accepting the last definition, hyperplasia mav be due to 

 an increased numljer of parenchymatous cells, or an increased 

 number of interstitial cells the two types l)eing called parench}'- 

 matous hvperplasia and interstitial hyperplasia respectively. 

 Parenchymatous hyperplasia and numerical hypertrophy are 

 sometimes used synonymously^ Interstitial hyperplasia is prac- 

 tically the same as fibrous hyperplasia. 



Parcnchxiiialous hyperplasia is not of common occurrence 

 It is usualiv either inherited or congenital. The descended or 

 scrotal testicle of single cryptorchids is usually enlarged I^ecause 

 of an increased amount of parenchyma and hence is an example 

 of parenchymatous hyperplasia. 



Interstitial h>"ptjrp 



FiK 108.— Hyperplasia Interstitial Testieular Cells. 



tissue. b. Seminiferous tubul.s not fully developed. 



