28 CELL DIFFERENTIATION AND THE ELEMENTARY TISSUES 



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 con junctival epithelium, covering the cornea 54. Lining 

 the vagina and the vaginal part of the cervix uteri. 



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

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



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

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



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. 



Transitional Epithelium. This is a stratified epithelium consisting of only 

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



M 



FIG. 29. Stratified Columnar Ciliated Epithelium from the Human Trachea. A mucous 

 (goblet) cell also is present. 



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 four layers 

 of polyhedral cells. This type of epithelium occurs in the bladder, ureter, 

 and pelvis of the kidney. 



