The Reticuloendothelial System (RES) is a network of cells and tissues that play a crucial role in the immune system. It primarily consists of specialized cells known as macrophages, which are found in various organs, including the liver, spleen, and lymph nodes. These cells help to identify and eliminate pathogens, dead cells, and other debris from the bloodstream. The RES is also involved in the processing of certain substances, such as iron and bilirubin. By filtering the blood and removing harmful materials, the RES contributes to maintaining overall health and supporting the body's defense mechanisms against infections and diseases.