Tissues: The Living Fabric

• Connective Tissue• Most abundant and widely distributed tissue type.– Four classes exist.• Common characteristics– Common origin• Develop from embryonic tissue called mesenchyme– Degree of vascularity• May be avascular, mildly vascularized or richly vascularized– Extracellular matrix• Non-living material surrounding cells• Composed of ground substance (IF, cell adhesion molecules, and proteoglycans)and fibers• Connective Tissue Cells• Adipocytes – Store fat• Macrophages – Phagocytes• Fibroblasts - Produce fiber– “-blast” = actively mitotic immature cell– “-cyte” = mature cell• WBCs – Immune cells– Plasma cells – Produce antibodies• Mast cells – Produce histamine and heparin• Connective Tissue Fibers• Three types of fibers exist– Collagen fibers (white fibers)• Most abundant and provides high tensile strength– Reticular fibers– Found in tendons and ligaments• Network of short, highly branched, collagenous fibers