Distribution of lymphatics in human palatine tonsils: a study by enzyme-histochemistry and scanning electron microscopy of lymphatic corrosion casts.

The distribution of lymphatics in human palatine tonsils was studied by enzyme-histochemistry for 5'-nucleotidase (5'-Nase) and scanning electron microscopy (SEM) of lymphatic corrosion casts. The palatine tonsils were found to possess lymphatics in the parafollicular area (i.e., interfollicular, interfolliculo-septal, and folliculo-septal area), in the connective tissue septa, and in the capsules, but not in the subepithelial area between the follicles and the follicle-associated epithelia or within the follicles. The tubular lymphatics originated some 200-300 microns below the epithelium and formed a three-dimensional network in the parafollicular area. Some lymphatics around the lower part of the follicle were flat, wide, and irregular in shape, and thus appeared to be lymphatic sinuses, referred to as perifollicular lymphatic sinuses. The lymphatics in the parafollicular area drained into the septal lymphatics, which ran rather straight in the connective tissue septa. The septal lymphatics finally gathered into the broader capsular lymphatics. Most of the septal and capsular lymphatics were endowed with valves. Our results indicate that lymphocytes and fluid from the follicles and the subepithelial region enter the perifollicular lymphatic sinuses and/or the interfollicular lymphatics, pass through the interfolliculo- and folliculo-septal lymphatics, and finally enter the septal and capsular lymphatics to leave the tonsil.