SQUAMOUS CELLS 41 



cells line cavities that normally communicate with 

 the air;' except the pleural, peritoneal, and synovial 

 sacs, and between the articulating cartilages of joints. 

 Epithelial cells are classified usually as: (1) squa- 

 mous, simple and stratified; (2) columnar, simple, modi- 

 fied, and stratified; (3) ciliated, simple and stratified; 

 (4) prickle cells; (5) goblet cells; (6) transitional cells; 

 (7) pigment; (8) neuro-epithelial ; (9) glandular. 



FTG 17 



\ 



Flat epithelial cells isolated from the oral mucous membrane of man. X 375 

 (Szymonowicz.) 



1. Squamous Cells. (a) Simple squamous cells con- 

 sist of a single layer of flattened elements, each con- 

 taining a nucleus, usually situated in the centre and 

 oval in form. They are found in the alveoli of the 

 lungs, ventricle of brain, descending limb of Henle's 

 loop in the kidney, and Bowman's capsule of kidney. 



(6) The stratified squamous cells consist of layers 

 of cells one on top of the other. The lowest layer, 

 the germinal stratum, is arranged in columns, those 

 above being polygonal. As the surface is reached 

 the cells become more flattened, forming the squames 

 or scales. These cells are usually found when they 

 afford the most protection, as the skin (epidermis) 



