Final answer:
The structure of a lymph node provides an environment for immune cells to interact with pathogens. The cortex contains germinal centers and the medulla consists of B cells and plasma cells.
Step-by-step explanation:
The structure of a lymph node allows lymphocytes and macrophages to perform their protective function by providing a specialized environment for immune cells to interact with pathogens. The lymph node is composed of different compartments, including the cortex and medulla, which contain various types of immune cells. Within the cortex, there are germinal centers where B cells rapidly divide and T cells and other accessory cells are present. The medulla consists of medullary cords of B cells and plasma cells, as well as medullary sinuses where lymph collects before leaving the node.