Reticular Connective Tissue
Reticular connective tissue is composed of reticular fibres, which are primarily made of type III collagen. These fibres form a delicate, mesh-like network that provides structural support for cells. Reticular connective tissue is abundant in organs related to the lymphatic and immune systems, such as the bone marrow, lymph nodes, and spleen. It is produced by specialised fibroblasts called reticular cells. The main function of reticular connective tissue is to create a supportive framework within these organs. The open structure allows for the movement of cells and fluids associated with immune responses and haematopoiesis.
Mononuclear Phagocyte System
The mononuclear phagocyte system (MPS) includes monocytes in the blood and macrophages found in various tissues, particularly those related to the lymphatic and immune systems. The MPS was first described by Ralph von Furth in 1969. Macrophages are derived from monocytes that originate in the bone marrow. Monocytes circulate in the blood and then migrate into tissues where they differentiate into macrophages. During this differentiation process, monocytes grow larger, increase their production of proteins, and develop more Golgi complexes and lysosomes, all of which contribute to their enhanced phagocytic capabilities.
Macrophages play a crucial role in the body's defence against foreign substances and pathogens. They are highly phagocytic, engulfing and destroying foreign particles, cellular debris, and microorganisms. Macrophages also contribute to tissue repair after injury. They have a wide range of shapes and sizes, reflecting their varying locations and functional states. Macrophages are often referred to as "histiocytes" by pathologists.