CHAPTER II 

 EPITHELIAL TISSUES 



TISSUES 



A tissue in the histologic sense is a collection of similarly specialized 

 cells united in the performance of a particular function, e.g., liver tissue. 

 In certain tissues the cells are joined together by an intercellular cement 

 substance, which is a secretion product of the cells themselves. 

 Through this cement may extend the so-called 'intercellular bridges' or 

 cytodesmata (Fig. 33), the minute intervening spaces forming delicate 



FIG. 33. GROUP OF EPITHELIAL CELLS FROM THE MALPIGHIAN LAYER OF 



THE SKIN. 

 The intercellular bridges are very distinct. Hematein and eosin. X 1,000. 



canaliculi, presumably for mediating the transfer of nutritive material 

 from cells more favorably placed with respect to the source of supply to 

 those less favorably located, e.g., epidermis; these bridges arise through 

 process of vacuolization in the exoplasm of adjoining cells, the walls 

 of the original vacuoles persisting as 'bridges.' Through such bridges, 

 fibrils may extend from cell to cell. Practically every tissue contains 



30 



