TKANSITIO^AL EPITHELIUM 



TRANSITIONAL EPITHELHIM. This variety of epithelium 

 resembles the preceding, in that it is composed of several cell 

 layers, the deeper cells of which are more nearly polyhedral but 

 are somewhat flat- 

 tened upon the free 

 surface. It differs, 

 however, in the num- 

 ber of cell layers, ^ v ^ ^ 

 , . , . , W il ^ A BK ^* 

 which is much less 



than is usual in the 

 preceding variety, 

 and in the character 

 of the superficial 

 cells. Transitional 

 epithelium is not 

 usually more than 

 from three to ten 

 cells deep, four to 

 six being the rule. 

 The numerical as 

 well as the actual 

 thickness of epithelial membranes is to a certain extent depend- 

 ent upon their state of tension during life ; thus the transitional 

 epithelium of the urinary bladder is much thicker when the organ 

 is collapsed than during distention. 



FIG. 28. TRANSITIONAL EPITHELIUM FROM A TRANSEC- 

 TION OF THE URETER OF AN INFANT. 



a, epithelium; ft, connective tissue. Hematein and eosin. 

 x 550. 



B 



FIG. 29. ISOLATED CELLS OF THE HUMAN URINE. 



A, from the vagina of a woman (stratified squamous epithelium) ; B, from the ureter 

 of a child (transitional epithelium); a, cells from the deep layers; 6, superficial cell- 

 Moderately magnified. 



