Which system is responsible for the body's defense against pathogens?

The immune system is responsible for the body's defense against pathogens, which include bacteria, viruses, fungi, and parasites. This complex network of cells, tissues, and organs works together to identify and eliminate these harmful invaders. Key components of the immune system include white blood cells, antibodies, the lymphatic system, and various organs such as the spleen and thymus.

When pathogens enter the body, the immune system recognizes them as foreign substances. It then triggers an immune response, which can involve both innate (immediate) and adaptive (long-term) mechanisms. The innate immune response provides a rapid, non-specific defense, while the adaptive immune response is more specific and creates a memory of the pathogens, allowing for a faster and stronger reaction upon re-exposure.

While the nervous, endocrine, and integumentary systems play important roles in maintaining overall health and homeostasis, they do not primarily function to defend against pathogens. The nervous system is involved in communication and coordination within the body, the endocrine system regulates hormonal functions, and the integumentary system (which includes the skin) provides a physical barrier but does not directly eliminate pathogens like the immune system does.