146 



FUNDAMENTALS OP^ STRUCTURE AND FUNCTION 



connecting cell with cell and making a pathway for the food sub- 

 stances. Small companion cells are attached to the sieve tubes. 

 The phloem is also provided with parenchyma and fibrous cells, 

 which give strength to the tubular bundle. 



The Tissues in Animals 



Although the histologist makes a much more detailed classification 

 of tissues, a convenient grouping for animals is the following : 



The Epithelial Tissues. Not only do these cells form the outer 

 layer of the animal body, but they also are responsible for the forma- 

 tion of such protective body structures as the calcareous shells of 



reticular odiposs 



emooth. 



grlonduP 



^ , fibrous Z,^ ..^ -- ^ ° ^' w^- -' .^^^l? 



stratifM ^.,^.:.:-:,^,:mm\ Striated: 



^m^mmSiim 



mm 



Columnar 



epithelial 

 ti55ue6 



vv ;.:>: -v: :. ;;,U^ loom. 



Yiyoline Cartilage 



supporting 



■tissues 



red. 

 © <!orpuscles 



circulcctorv 





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Types of animal tissue cells. Into how many groups may they be classified ? 



clams and oysters, the chitinous covering of the insect, or the outer 

 covering of the crayfish. These tissues line all body surfaces as 

 well as the digestive tract and other inpocketings of the outer body 

 covering. They are of the utmost importance because they also 

 form the glands of the body, structures which secrete, for example. 



