CELLULAR DIFFERENTIATION 



49 



primary work as a protective layer, the epithelium may have 

 a glandular function, being favorably situated for the final 



LA. 



FIG. 16. Various kinds of epithelial cells (semi-diagrammatic). A, columnar; B, cuboidal; 

 C, pavement; D and E, ciliate (sectional views). In F is shown the surface view of pavement 

 epithelium. cl. t cilia; cu., cuticula. 



Questions on the figures. For what different uses would you judge these 

 variously shaped epithelial cells to be suited? Under what circumstances and on 

 what surfaces would you expect to find each type? Compare with your reference 

 texts and see if they are so found. Under what circumstances is a cuticula to be 

 expected? Where would it be a disadvantage? What are cilia? 



- < FIG. 17. 



,'OL 



PIG. 17. Glandular epithelium, a, goblet or slime cells, unicellular glands; 6, similar cells 

 which have become depressed below the surface, and empty their secretion through a duct. 



Questions on the figures. Are the glandular cells modified epithelial cells? In 

 what respects do they differ from the cells about them ? 



elimination of products from the body. Since it is especially 

 exposed it is the layer best adapted by position to receive those 

 external stimuli which we know to play such an important r61e 



