Final answer:
Bronchopulmonary (hilar) lymph nodes are associated with the lungs and form part of the immune system's defenses against inhaled pathogens.
Step-by-step explanation:
The Bronchopulmonary (hilar) lymph nodes are associated with the lungs. These lymph nodes are part of the bronchus-associated lymphoid tissue (BALT) which consists of lymphoid follicular structures found along the bifurcations of the bronchi, and between the bronchi and arteries.
They are involved in defensive mechanisms against inhaled pathogens. Unlike the spleen and other lymph nodes, they have a less-organized structure typical of the other lymphoid nodules located in respiratory and digestive tracts.