EPITHELIAL TISSUES 



Bepresentatives of all of the fundamental tissues are generally found 

 in all histologic preparations, or tissues in a general sense. Cells vary 

 greatly both from the standpoints of shape and contents in the various 

 tissues both- depending upon the types and phases of function. The 

 more usual form variations include: (a) spheroidal, spherical (e.g., em- 

 bryonic cells and egg cells, Fig. 1, chap. 1), polyhedral (spherical cells 

 modified by pressure from adjacent cells, e.g., liver cells, Fig. 37) ; (b) 

 scalelike or squamous (e.g., super- 

 ficial cells of mucous membrane of 

 mouth, Fig. 36, a) ; (c) columnar, 

 prismatic or cylindrical (e.g., cells 

 lining intestine, Fig. 38. b). Col- 

 umnar cells, when very short, are 



FIG. 37. POLYHEDRAL EPITHELIUM, 

 FROM A SECTION OF THE HUMAN 

 LIVER. 

 The central blood capillary contains 



one leukocyte, and its wall contains the 



nucleus of a flattened endothelial cell. 



Hematein and eosin. X 550. 



FIG. 38. GOBLET AND COLUMNAR CELLS 

 FROM THE LARGE INTESTINE OK THE 

 CAT. 

 A, Goblet cells; B, isolated columnar 



cells. X 900. 



usually designated cubical or cuboidal (e.g., bronchioles and rete testis, 

 Fig. 43) ; intermediate lengths may be designated either tall cuboidal or 

 short columnar; when modified by confinement in an alveolus into a 

 pyramidal shape as in glands, they may be called pyramidal or 'glandu- 

 lar' (Fig. 46). Glandular cells, moreover, are characterized also by an 

 internal differentiation commonly expressed in the form of granules or 

 filaments. Columnar cells may be further modified by the appearance of 

 cilia into ciliated epithelium (e.g., trachea, bronchial tube. Fig. 52), or of 

 mucus into goblet cells or 'unicellular glands' (e.g., intestine, Fig. 38, a) ; 

 or as specialized receptors for stimuli of special sense they may become 

 modified as neuro-epithelium (e.g., certain cells of eye, ear, nose and 

 tongue). 



