ELEMENTS OF PHYSIOLOGY 



59. Epithelial Tissue. Covering the surface of the 

 body and lining every cavity and tube of its interior, is a 

 tissue consisting of one or more layers of dis- 

 tinct cells, forming what is called epithelial 

 tissue. You learned in Chapter I that from 

 it the hair and nails are produced. It is per- 



haps the simplest of 

 the tissues, consist- 

 ing merely of cells 

 packed closely to- 

 gether, and united by 

 a very small amount 

 of a cement sub- 

 stance of albuminous 

 nature. The cells 

 may be in a single FlG '|^~ The 

 layer, as in the mu- Epithelial ^ at 

 cous membrane of <A and * con - 



nective and fatty 



the intestine (Fig. 

 28), or in many lay- 



FlG. 35. Connective or Sup- . 



porting Tissue taken from be- ers, as in the epl- 



neath the skin. dermis. No blood 



Notice that there is a loose network , **.!. 



of wavy bundles of fibers, also VCSSClS paSS HltO tilC 



a network of threadlike fibers^ epithelial tisSUC J the 

 These fibers were probably formed 



by the cells which you see lying cells derive their 

 in the meshes. 



nourishment by ab- 



sorbing it from the watery portion of the 

 blood exuded into the adjacent tissues. The 

 epithelial tissue grows by subdivision of the 

 cells of the lowest layer. When the nu- 

 cleus has disappeared, the cells die and 

 flatten and become mere horny plates, easily 

 detached; and thus the outer cells are con- 



tissue below. 



FIG. 37. Con- 

 nective Tissue. 

 (//), Epithelial. 

 (7),intheWall 

 of the Eyeball. 



stantly wearing away as you learned when studying the 

 skin. 



