60 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



the epithelial cells rest, although at times flattened 

 connective-tissue cells seem to enter into its forma- 

 tion. The membrana propria is a connective-tissue 

 production consisting of connective-tissue cells, 

 fibers, and blood- and lymph- vessels. Mucous mem- 



Demilune of Heidenhain. 



Fig. 26. Cells from different glands : a, Pancreas; b, submaxillary 

 gland; c, liver. 



branes line cavities or tubes that communicate with 

 the surface of the body, such as the alimentary canal, 

 respiratory tract, and urogenital system. 



Serous Membrane. A serous 

 membrane has the same histo- 

 logical elements as the mucous 

 membrane. The epithelial lining 

 is simple squamous, and these 

 cells secrete a serous fluid, more 

 viscid and more of a lubricant 

 than mucus. Serous membranes 

 enclose cavities that do not com- 

 municate with the surface of the 

 body, as the pleural, pericardial, and peritoneal 

 cavities and cavities of joints, forming in the latter 

 case synovial membranes. Sheaths or bursae of 

 tendons have serous membranes. 



Cell empty 

 of secretion. 



Fig. 27. Goblet or 

 mucous cells from intes- 

 tine. 



