COLUMNAR EPITHELIUM. 



31 



cubical shape, and occurs in the tubules of the testis and in the 

 alveoli of the thyroid gland. 



FIG. 18. Isolated cells of squamous epithelium (surface cells of the stratified 

 squamous epithelium lining the mouth) : a, a, cells presenting under surface ; 

 6, cell with two nuclei (Huber). 



Columnar Epithelium (Fig. 20). Columnar epithelium is 

 sometimes described as cylindrie epithelium. The cells are of a 

 prismatic shape, and usually rest upon 

 a basement-membrane. When looked 

 at from the free end, they present the 

 appearance of a mosaic ; when ob- 

 served from the side, the free edge 

 is seen to be striated. 



This variety of epithelium lines 

 the stomach and intestines, and the 

 glands which open into these cavi- 

 ties. It covers the mucous mem- 

 brane of most of the urethra, the vas FlG - i9;-Surface view of squa- 

 -, f, ,-* i j mous epithelium from skin of a 



deferens, prostate, Cowper's glands, frog; x400(B6hm and Davidoff). 

 and the ducts of most glands. The 



germinal epithelium which covers the ovary is of this type. 

 Goblet-cell (Fig. 22). A peculiar modification of columnar 



Goblet-cell. 

 Cuticular border. 



FIG. 20. Simple columnar epithelium from the small intestine of man : o, isolated 

 cells ; b, surface view ; c, longitudinal section (Huber). 



