Final answer:
The spleen is the single largest mass of lymphatic tissue in the body, acting as a blood filter and a vital participant in the immune response against blood-borne pathogens.
Step-by-step explanation:
The single largest mass of lymphatic tissue in the body is the spleen.
The spleen is considered a major secondary lymphoid organ, spanning about 12 cm in length and located on the lateral border of the stomach, attached by the gastrosplenic ligament. Possessing a dark red color due to its extensive vascularization, the spleen earns its reputation as the 'filter of blood.'
It is equipped with macrophages and dendritic cells that remove microbes and other foreign materials, including outdated red blood cells, effectively cleansing the circulatory system. Beyond its filtering role, the spleen also initiates immune responses to pathogens encountered in the blood, making it crucial for combating infections. It is different from lymph nodes, which are smaller but numerous lymphatic tissue collections strategically placed along the lymphatic vessels to filter lymph.