Which system is tasked with protecting the body from external threats and aiding in healing and repair?

The immune system is responsible for defending the body against external threats such as pathogens, including bacteria, viruses, fungi, and parasites. It identifies these foreign invaders and mounts a response to eliminate them, which includes producing antibodies and activating various types of immune cells. In addition to its protective function, the immune system plays a crucial role in healing and repair processes. When tissues are damaged due to infection or injury, immune cells are activated to facilitate the healing process, including fighting off infection and repairing tissue damage. This dual capacity to protect and heal makes the immune system vital for maintaining overall health and well-being.

The other systems mentioned do not primarily focus on protection and healing. The endocrine system regulates hormones that control many body functions, the respiratory system is involved in gas exchange and breathing, and the digestive system is focused on processing food and absorbing nutrients. Each of these systems has its own specific functions that do not encompass the protective and restorative roles carried out by the immune system.