ABSTRACT
The lymphoreticular system is involved in the defence of the body against microorganisms and foreign substances – i.e. the immune response. The system consists of two discrete organs, the thymus and spleen, together with an extensive network of lymph nodes which is distributed throughout the body. In addition, there is diffuse lymphoid tissue, which is closely associated with mucosal surfaces, most prominently in the gut (p. 243), and also in the upper respiratory tract in Waldeyer’s ring – the tonsils and adenoids. Lymphoid cells are also well represented within the bone marrow. This is, of course, the site of haemopoiesis – the process by which mature blood cells are produced.
