On the functional macro- and microstructure of the lymphatic system. In memory of Rudolf Virchow (1821-1902).

The mutual basis of the unspecific as well as the specific defense system is the reticular connective tissue which is closely related to the mesenchyma. Its fixed and free elements make up the stroma and "parenchyma" of the lymphatic organs. As carriers of specific defense the immunocompetent T- and B-lymphocytes are "stamped" in the lymphoepithelial organs and the embryonic liver. The proliferation and differentiation of the immunocytes and plasma cells which are responsible for the cellular and humoral immunity ensues in the lymphoreticular organs (lymph nodes and spleen). These "lymphatic organs in a narrow sense" which are also the focal points of the RES and RHS are still of major interest. The topography, macro- and micromorphology of the lymphoreticular organs are therefore the actual topic of this review which also covers the lymph vessel system with due attention. The lymph nodes are of pre-eminent interest: It is the primary intent of this paper to improve the understanding of their practical importance for the pathophysiology of the lymphatic system from the standpoint of normal functional anatomy. For lack of space and time alone, it was impossible to include a discussion of the just so acute and problematic morphobiology of the spleen.