Answer
Pathogens that breach the protective epidermis will encounter phagocytes and other defensive cells that wander through the loose connective tissue of reticular connective tissue.
Reticuloendothelial system
Also known as mononuclear phagocyte system or macrophage system. It is a part of immune system consisting of phagocytic cells especially monocyte and macrophages that accumulate in lymph nodes and spleen. Kuffer cells of liver and histocytes are also part of this system.
Formation of cells
The monocytes formed in the bone marrow diffuse into blood stream and transported to tissues where it develop into macrophages or histocyte. The life cycle of monocyte is one day while that of macrophage is several months to year. Macrophages wander in liver (kufffer cells), lungs (alveolar macrophages), central nervous sytem (microglia). They are also part of cell mediated immunity and humoral mediated immunity.
Role of phagocytic cells
They have an important role against bacteria, fungi, viruses etc.