EPITHELIAL TISSUES. &5 



lying blood-capillaries. The pyramidal extensions of the epithelium 

 between the papillae are designated inter papillary epithelial processes. 

 In regions where the stratified squamous epithelium consists of 

 many layers, the prickle cells, intercellular bridges, and the inter- 

 cellular spaces are especially well developed. These spaces facili- 

 tate the passage of the lymph-plasma to the more superficial layers 

 of cells. 



(U] Transitional Epithelium. Transitional epithelium is a 

 stratified epithelium occurring in the pelvis of the kidney, the ure- 

 ters, bladder, and the posterior portion of the male urethra. It is 

 composed of four to six layers of cells and rests on a connective 

 tissue free from papillae. In sections the cells of the deeper layers 

 appear to be of irregularly columnar, cubic or triangular shape. The 





j ;-'. ' 



Fig. 44. Isolated transitional epithe- 



lial cells from the bladder of man : a, v, 



c, d, Large surface cells, rand d presenting child. 



the pitted undersurface ; <?, variously shaped 



cells from the deeper layers. 



"& ' 



Fig. 45. Cross-section of transitional 

 epithelium from the bladder of a young 



cells forming the superficial layer are large, somewhat flattened cells, 

 with convex free surfaces, often possessing two, sometimes three, 

 nuclei. They cover a number of the cells of the layer just beneath 

 them, their under surfaces being pitted to receive the upper ends of 

 the deeper cells. In teased preparations the cells of the deeper 

 layers appear very irregular, often showing ridges or variously 

 shaped processes. (See Fig. 44.) 



(c) Stratified Columnar Epithelium. In this type the super- 

 ficial layer consists of columnar cells, the basal ends of which are 

 usually somewhat pointed, or may branch. The deeper cells, which 

 may be arranged in one or more layers, are of irregular, triangular, 

 polyhedral, or spindle shape. It is found in the larger gland ducts, 

 olfactory mucous membrane, palpebral conjunctiva, portions of the 



