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Connective tissue Structure Function Extracellular matrix 1. Ground substance 2. Fibers (collagen, reticular, and elastic) Collagen fibers Reticular fibers Elastic fibers Fibroblast the predominant cell type, are responsible for synthesis of collagen, elastic and reticular fibers, and much , if not all, of the ground substance . Morphology : appear spindle-shape with their numerous flattened processes and oval nuclei. Constitute the major cellular component. Fibroblast Macrophage (histocytes) are derived from monocytes in bone marrow Morphology : irregular shape, smaller, darker, and denser than those of fibroblast with oval nuclei. Mast cells located in the vicinity of blood vessels, may be recognized by their size. Morphology : round, large, centrally located nuclei, numerous small granules in their cytoplasm. Fat cells (adipocytes) may form small clusters in loose connective tissue they store lipids and form adipose tissue, which protects , insulates and cushions organs of the body. Morphology : resembling round ,eccentric nucleus, empty spaces bordered by a thin rim of cytoplasm may also be present. Fat cells (adipocytes) plasma cell are the major cell type present during chronic inflammation Morphology : small, round cells with round , acentric nuclei, whose chromatin network presents a clockface (cartwheel) appearances. Also lymphocytes , neutrophils, and occasional eosinophils also contribute to the connective tissue Connective tissue types: I. Embryonic connective tissue: A) Mesenchymal connective tissue Appearance : the matrix empty-looking , contain fine reticular fibers. Small blood vessels are evident. Mesenchymal cells are present , stellate to spindle- shape , have processes that touch one another . pale scanty cytoplasm with large clear nuclei. Indistinct cell membrane. B) Mucous connective tissue. Appearance :when compared with mesenchymal C.T., the intercellular space is filled with coarse collagen bundles , irregularly arranged , matrix is jelly- like material. Fibroblast , consist the major cellular component. these cells are resemble or identical with mesenchymal cells when viewed with a light microscope. II. Connective tissue proper : A. Loose ( Areolar) connective tissue Appearance : Slender bundles of collagen fibers are intertwine by numerous thin, straight , long, branching elastic fibers embedded in a watery matrix. reticular fibers , also present , are usually not visible in section stained with hematoxylin and eosin. A. Loose ( Areolar) connective tissue The most common cell types are fibroblasts, macrophages, mast cells, occasionally fat cells and in some subepithelial connective tissue ( lamina propria) of intestines, plasma cells and leukocytes are commonly found. B) Reticular connective tissue . Appearance : reticular fibers constitute the major portion of the intercellular matrix with use of a sliver stain. Reticular cells are found only in reticular C.T. they are stellate in shape they possess large , oval, pale nuclei, and their cytoplasm is not easily visible with light microscope. C) Adipose tissue Appearance : Unlike other connective tissue , adipose tissue is composed of adipose cells so closely packed to gather. Groups of fat cells are subdivided into lobules by thin sheaths of loose connective tissue septa housing mast cell, endothelial cells of blood vessels. Each fat cell is invested by reticular fibers, which , in turn , are anchored to the collagen fibers of connective tissue septa.
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