Final answer:
The medullary cords of a lymph node primarily contain B cells and plasma cells, which are crucial to the adaptive immune system, with macrophages located in the medullary sinuses.
Step-by-step explanation:
The medullary cords of a lymph node contain B cells and plasma cells. These cells are vital components of the adaptive immune system. The B cells within these cords can differentiate into plasma cells, which are responsible for producing antibodies. Additionally, the medullary sinuses, which are the spaces between the cords, are populated by macrophages that play a phagocytic role in the immune response. They help to filter the lymph and remove any foreign particles or pathogens before the lymph exits the node through the efferent lymphatic vessels.