STRATIFIED EPITHELIUM 



2 9 



surface, gradually altering in shape and chemical composition until they 

 die and are cast off from the surface. 



Stratified squamous epithelium is found in the following situations: i. 

 Forming the epidermis, covering the whole of the external surface of the body; 

 2. Covering the mucous membrane of the nose, tongue, mouth, pharynx, and 

 esophagus; 3. As the conjunctival epithelium, covering the cornea; 4. 

 Lining the vagina and the vaginal part of the cervix uteri. 



FIG. 27. Vertical Section of the Stratified Epithelium Covering the Front of the 

 Cornea. Highly magnified. (Schafer.) c, Lowermost columnar cells; p, polygonal cells 

 above these ; fl, flattened cells near the surface. The intercellular channels, bridged by 

 minute cell processes, are well seen. 



Stratified Columnar Epithelium. In this type of epithelium, the surface 

 cells alone are columnar, the deeper cells being irregular in shape. From 

 the surface cells long processes extend down among the underlying cells. 

 This type of epithelium is usually ciliated, as in the trachea, bronchi, etc., 

 but may be non-ciliated, as in portions of the human male urethra. 



a^i^^^'^^M 



FIG. 28. Epithelial Cells from the Stratum Spinosum of the Human Epidermis, Showing 

 "Intercellular Bridges." X 700. (Szymonowicz.) 



Transitional Epithelium. This is a stratified epithelium consisting of 

 only three or four layers of cells. The superficial cells are large and flat, 

 often containing two nuclei. The under surfaces of these cells are hollowed 

 out, and into these depressions fit the large ends of the pyriform cells which 

 form the next layer. Beneath the layer of pyriform cells are from one to 



