Which term describes the network that defends the body against infection and disease?

• A. Cardiovascular system
• B. Endocrine system
• C. Lymphatic system
• D. Digestive system

Answer: (C)

The lymphatic system functions as the body's defense network against infection and disease. It includes vessels and immune organs like lymph nodes, the spleen, thymus, and bone marrow, all working together to detect and respond to pathogens. Lymph carries immune cells such as lymphocytes and macrophages, and lymph nodes act as filtering hubs where pathogens are exposed to these cells so an immune response can begin. The spleen helps cleanse the blood of invaders, and the thymus trains T cells to recognize threats. This system also helps return excess fluid to the bloodstream, supporting overall immune surveillance. The other systems have different primary roles—circulating blood, producing hormones, or digesting food—so they aren’t the networks best described as defending against infection.