A comparative histological study of the surface epithelium and high endothelial venules in the subepithelial compartments of human nasopharyngeal and palatine tonsils.

OBJECTIVE To compare the thickness and organization of surface epithelium, and high endothelial venules in subepithelial compartments of human nasopharyngeal and palatine tonsils, with reference to functional differences. STUDY DESIGN Comparative cross-sectional. PLACE AND DURATION OF STUDY The Anatomy Department of CPSP Regional Centre, Islamabad, from January to December 2005. METHODOLOGY Thirty samples each of human nasopharyngeal, right palatine and left palatine tonsils were collected by convenience sampling technique. Haematoxylin and eosin stained paraffin sections were examined for surface epithelium. Thickness of stratified squamous and pseudostratified ciliated columnar epithelium was measured, while organization was observed in case of stratified squamous. The high endothelial venules in subepithelial lymphoid compartments were counted. RESULTS The surface epithelium of nasopharyngeal tonsils (stratified squamous and pseudostratified columnar inclusive) was 63.21+1.93 microm, and that of palatine (stratified squamous) was 143.99+5.94 microm thick (p<0.001). The mean count of high endothelial venules in subepithelial compartments of nasopharyngeal was 1.15+/-0.06 and that of palatine tonsil was 0.93+0.08 (p=0.042). Organization of stratified squamous epithelium was poor in 26 out of 30 nasopharyngeal, and well in all palatine tonsils (p<0.001). CONCLUSION The surface epithelium of nasopharyngeal tonsil being thinner and poorly organized than that of palatine tonsil might act as a less effective barrier between the antigenic stimulus and subepithelial lymphoid compartments. This may contribute towards higher level of immune response by these compartments of the former, which is endorsed by higher number of high endothelial venules as compared to the latter.