What structures filter out harmful particles from lymph before it re-enters the bloodstream?

Lymph nodes play a crucial role in the immune system by filtering lymph, which is a fluid that contains infection-fighting white blood cells, among other substances. These small, bean-shaped structures are strategically located throughout the body and act as checkpoints in the lymphatic system. As lymph travels through these nodes, it is exposed to immune cells that can identify and respond to harmful particles, such as bacteria, viruses, and cancer cells. The lymph nodes trap these pathogens and facilitate their destruction through various immune responses, ensuring that only clean lymph re-enters the bloodstream. This filtration process is vital for maintaining the body's health and preventing the spread of infections.

In contrast, the thymus is primarily involved in the maturation of T-cells, a type of white blood cell, while the spleen processes blood and helps remove old or damaged blood cells. Tonsils help guard against infections entering through the mouth and throat but are not part of the lymphatic system's filtration process in the same way as lymph nodes.