(Posted:16-Jul-2015)

The connective tissue owes its name because it binds other tissues of the body.The connective tissue is derived from the embryogenic mesoderm.The connective tissue has two components-cells and intracellular substances. Cells: Seven principal types of cells are found in the ordinary connective tissue: (1)Fibroblast,(2)Macrophage,(3)Mast cells,(3)Pigment cells,(4)Reticular cells and(7)Fat cells. (1)Fibroblast: These cells are numerous and derived from undifferentiated mesenchymal cells.Each cell is flattened or fusiform in shape with a centrally placed nucleus and present numerous processes. When the fibroblasts become old and inactive they are converted into fibrocyte. Functions: a)The fibroblast help in formation of collagen fibers. The fibroblast secrets in some situations proteoglycans,reticular for reticular fibers and elastin for elastic fibers. b)They help in healing of wounds by continued proliferation and subsequent conversion into fibrocytes. c)The fibroblast act as stem cells for other cellular components of the connective tissue. 2)Macrophage: The macrophage are derived from the undifferentiated mesenchyme or from the fibriblast or from the monocytes of the blood. They are distributed widely in different parts of body and belong to mononuclear phagocytes system which subserves an important apparatus for defensive mechanism of the body. Macrophage distributed in connective tissue,blood as the monocytes,sinusoides of the liver,lymphoid tissue,lymph node,lung alveoli,brain and spinal cord. Function: a) The macrophage phagocytose and digest particulate organic materials,foreign bodies or invading microorganism and thereby eliminate them from the body to avoid injurious effects. b)The macrophage ingest non-specific antigens.Thereafter the antigens may be destroyed or they are transferred after modification to the immunologically competent cells of T-lymphocytes or B-lymphocytes. 3)Plasma cells: These cells are numerous in the mucous and submucous coats of the gut and in the greater omentum.Each cell is rounded in shape without any process and presence granular cytoplasm which is stained with basic dyes. Function: a)The plasma cells liberate humoral antibodies to counter act the action of antigens,and help in defense mechanism of the body. b)The plasma cells are derived from B-lymphocytes particularly when the latter are exposed to antigens. 4) Mast cells: Mast cells are present in the fibrous capsule of the liver ,along the blood vessels,beneath the mucosa of alimentary tract and respiratory tract and in other parts of the body. Functions: a)The mast cells liberate heparin which is anticoagulant in function. b)Mast cells produce histamine,which promotes capillary leakage and edema and contraction of smooth muscles. 5)Pigment cells: Pigment cells are also known as the melanocytes are present in the epidermis of the skin,in the irish and choroid coat of the eyeball.The melanocytes are derived from the neural crest epithelium. Function: In the skin,the melanocytes protect against the cosmic rays of the sun. 6)Reticular cells: These are present in the reticular connective tissue.They produce reticular fibers to which the cells are attaced. Functions: a)Phagocytosis. b)Act as a stem cells for the cellular constituent of the blood. 7)Fat cells: Fat cells or adipocytes are numerous in the adipose tissue.Each cell is spherical or polygonal,consists of peripheral rim of cytoplasm with an ecentric nucleus and contains a large central lobule of fat.