What system in the body defends against infections?

The immune system is the body's primary defense against infections. It comprises a complex network of cells, tissues, and organs that work together to identify and eliminate pathogens such as bacteria, viruses, fungi, and parasites. The immune response involves various components, including white blood cells, antibodies, and specialized organs such as the spleen and lymph nodes that help monitor and respond to threats.

When a pathogen enters the body, the immune system activates its defense mechanisms, which include recognizing foreign invaders and mounting an attack to neutralize or destroy them. This ability to detect and respond to infections is vital for maintaining health and preventing disease.

In contrast, while the circulatory system is responsible for transporting blood, nutrients, and oxygen throughout the body, it does not specifically target infections. The nervous system primarily handles communication within the body and responds to environmental stimuli, while the endocrine system manages hormone production and regulation, influencing various bodily functions but not directly fighting infections. Thus, the immune system stands out as the definitive defender against infections.