Connective tissue

Connective tissue

Connective tissue is formed primarily of extracellular matrix, consisting of ground substance, and fibers, in which various connective tissue cells are embedded.

Function.
Connective tissue supports organs and cells, acts as a medium for exchange of nutri¬ents and wastes between the blood and tissues, protects against microorganisms, repairs damaged tissues, and stores fat.

A. Ground substance is a colorless, transparent, gel-like material in which the cells and fibers of connective tissue are embedded. It is a complex mixture of glycosaminoglycans, proteoglycans, and glycoproteins .
Ground substance serves as a lubricant, helps prevent invasion of tissues by foreign agents, and resists forces of compression.
Frequently, amorphous ground substance macromolecules are bound to fibrous compo¬nents.
Mineralization often occurs in connective tissue amorphous ground substance. The minerals contribute hardness to mineralized connective tissues such as bone, dentin, and enamel.
The extracellular matrix provides a medium for the transfer of nutrients and waste materials between connective tissue cells and the bloodstream.

B. Fibers (collagen, reticular, and elastic) are long, slender protein polymers present in differ¬ent proportions in different types of connective tissue.
Blood contains an extracellular fibrous component called fibrinogen, which is a potential group of fibers. When blood clots, the potential fibers of fibrinogen are converted into actual fibers of fibrin.


c. Cells : Connective tissue resident cells vary considerably and may include mast cells, macrophages, plasma cells , fibroblasts, chondro¬blasts , chondrocytes, osteoblasts , osteocytes, adipocytes, and macrophages.
Connective tissue immigrant cells can include all of the formed cellular elements of the blood with the exception of erythrocytes. When injury or inflammation damages tissue, leukocytes (e.g., monocytes), lymphocytes, and phagocytic granulocytes (e.g., neutrophils, eosinophils, basophils) leave the circulation and join fibroblasts and other connective tissue resident cells to repair damage and combat microorganisms that cause inflammation.