220 



HISTOLOGY 



Frequently they have been called amygdala (almonds), but the older 

 Latin term for them is tonsilla (a stake to which boats are tied). They 

 are covered by the mucous membrane or tunica mucosa, which throughout 

 the digestive tract consists of several layers. The soft moist entodermal 

 epithelium rests on a connective or reticular tissue layer, the tunica propria. 

 A structureless basement membrane, the membrana propria, is often pres- 

 ent immediately beneath the epithelium. The epithelium, membrana 

 propria, and tunica propria together form the mucous membrane, which 

 in dissection would be stripped off as a single structure. Beneath it, and 

 sometimes not clearly separable from the tunica propria, is the submucous 



FIG. 209. VERTICAL SECTION OF A HUMAN PALATINE TONSIL. 



a, Stratified epithelium; b, basement membrane; c, tunica propria; d, trabeculae; e, diffuse lymphoid 

 tissue; f, nodules; h, capsule; i, mucous glands; k, striated muscle; 1, blood vessel; q, pits. (From 

 Radasch.) 



layer, or tela submucosa. It is a vascular connective tissue, by which the 

 mucous membrane is attached to underlying muscles or bones. All the 

 layers named are involved in the tonsils which, however, are essentially 

 lymphoid accumulations in the tunica propria. 



The epithelium of the palatine tonsils is a stratified epithelium of 

 many layers, with flattened cells on its smooth free surface, and columnar 

 cells beneath. Its attached surface is invaded by connective tissue ele- 

 vations or papillae, so that it appears wavy in sections (Fig. 209). The 

 stratified epithelium lines from ten to twenty almost macroscopic depres- 

 sions, called tonsillar pits or fossula (crypts). These are irregularly tub- 

 ular and sometimes branched. Many lymphocytes penetrate between 

 the epithelial cells and escape from the free surface into the saliva, be- 

 coming "salivary corpuscles." In places the tonsillar epithelium is so 

 full of lymphocytes as to appear disintegrated, a condition which was 



