28 



HISTOLOGY. 



the nucleus. In Fig. 26 there is both a surface view and a section of 



simple columnar epithelium. Often columnar cells are nearly cuboidal 



and are described as low columnar. 



Gradations between all the types 



described are to be expected. (The A 



following synonyms are in common 



Cuticula. 



Cross section 

 of a 

 terminal bar. 



FIG. 25. 



A, Surface view of mesothelium from the mesen- 

 tery; B, surface view of endothelium from an 

 artery. 





FIG. 26.- SIMPLE COLUMNAR EPITHELIUM FROM 

 THE INTESTINAL VILLUS OF MAN. 



A, Surface view; B, vertical section. The promi- 

 nent cell outlines in A are due to terminal bars, 

 shown in cross section at the left of B, and in 

 side view at the right. 



use: cylindrical for columnar; pavement for cuboidal or flat; and 

 squamous, meaning scale-like, for flat.) 



NUMBER OF LAYERS. 



A simple epithelium may be so arranged that it appears to consist of 

 several layers (Fig. 27). All of the cells start from the connective tissue 



I I MM 



FIG. 27. DIAGRAM OF PSEUDO- 

 STRATIFIED EPITHELIUM. 



FIG. 28. STRATIFIED EPI- 

 THELIUM FROM THE 

 HUMAN LARYNX. X 

 240. 



Columnar cells; 2, poly- 

 gonal cells; 3, flat 

 (squamous) cells. 



FIG. 29. DETACHED SOUA- 

 MOUS CELLS FROM THE 

 MOUTH. 



below, but may fail to reach the free surface. Their nuclei are at different 

 levels. Such pseudo-stratified epithelium is found in parts of the respira- 



