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Vinnytsya National Pirogov Memorial University Histology Department CONNECTIVE TISSUE
as. Hrytsenko A.S.
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Connective tissues is a complex of mesenchyme derivatives, consisting of cells diferons and big quantity of extracellular matrix (fibers and ground substance); comprises more than 50% of human body mass; It participates in formation of organs, layers between other tissues, derma of a skin, skeleton.
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functions of connective tissue
1. Support: formation of stroma of inner organs; separation of structural-functional units of other tissues and organs; maintenance and coordination of all body functions. 2. Defense: physical - the viscosity of the extracellular matrix slows the spread of many bacteria and foreign particles; sheets of tightly packed collagen fibers, as in organ capsules, help to confine local infections; immunologic - cells of connective tissue activate local immune responses (inflammation). 3. Repair: injury stimulates proliferation of fibroblasts, which rapidly form collagenous matrices that close wounds and form scars. 4. Storage: reserves of water and electrolytes, especially sodium; energy reserves in the form of lipids are stored in adipocytes. 5. Most blood and lymphatic vessels and peripheral nerves are surrounded by loose connective tissue.
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CLASSIFICATION OF inner tissues:
Blood and lymph Sceletal tissue: Bone Cartilage Connective tissue proper: loose connective tissue dense connective tissue: dense irregular connective tissue dense regular connective tissue Connective tissue with special properties: Reticular Mucoid Pigmented Adipose: White adipose Brown adipose
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LOOSE CONNECTIVE TISSUE
Consists of: Cells; Extracellular matrix: Fibers; Ground substance.
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CELLS OF CONNECTIVE TISSUE
Fixed (permanent resident) cells are native to the tissue in which they are found: Fibroblasts Myofibroblasts Fibroclast Macrophages Monocyte-derived phagocytes Mast cells Adipose cells Pericytes Wandering (transient) cells are immigrant cells, usually from blood or bone marrow: Plasma cells Lymphocytes Monocytes Neutrophils Eosinophils Basophils
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FIBROBLASTS Structure: size of the cell is 40-50 mcm;
is stellate shape; has long cytoplasmic processes; has large, ovoid, pale-staining nucleus with 1-2 big nucleolus; contains rough endoplasmic reticulum and Golgi complex; Function; synthesize, secrete, and maintain all major extracellular matrix components: synthesis GAG (glycosaminoglycan) of the intercellular ground substance; synthesis procolagen and elastin FIBROBLASTS Fibroblast differon: stem cell→unmature fibroblast →mature (active) fibroblast →myofibroblast, fibroclast and fibrocyte; are the principal and most common cells in connective tissue; are mitotically active; There are two types of these cells: Active (fibroblast); Quiescent (fibrocyte)
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FIBROCYTES spindly shaped; has an acidophilic cytoplasm ;
contein small amount of rough endoplasmic reticulum; contein small amount of other organelles; synthetic processes are decreased; may revert to the fibroblast state and participate in tissue repair.
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Unmature fibroblast is mitotically active cell;
size of the cell is mcm; cytoplasm is slightly basophilic; cytoplasm is rich in RNA molecules; has short processes and round or oval-shaped nucleus; rouph endoplasmic reticulum and Golgi complexes are undeveloped; production of collagen and other matrix components very poor.
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Myofibroblast displays properties of both fibroblast and smooth muscle cell; have the morphologic characteristics of fibroblasts but contain increased amounts of actin and myosin microfilaments; is responsible for wound closure and contraction; is found in the periodontal ligament, where it probably assist in tooth eruption.
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Fibroclast has high phagocytic and hydrolytic activity, share in resorption of extracellular matrix in an involution of organs; combine features of mature fibroblast and lysosomes with hydrolases.
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macrophages Is derived from monocytes that infiltrate connective tissue and develop into phagocytes; large, stellate cells; contain a large Golgi, rough and smooth endoplasmic reticulum, mitochondria, secretory vesicles and lysosomes; Functions: phagocytosis; presenting lymphocytes with concentrated antigens; removing foreign substances and cell debris.
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Mast cell derive from bone marrow precursors;
large (20 to 30 mcm) cells; has electron-dense basophilic granules; have many small plasma membrane folds; well-developed Golgi complex; small central nucleus; have surface receptors for the IgE antibodies that trigger degranulation, the exocytosis of the granule; Granules contain : heparin; histamine; eosinophilic chemotactic factor of anaphylaxis (ECF- A); neutral proteases; neutrophil chemotactic factor (NCF); arachidonic acid precursors: leukotrienes (LTD4, LTE4 and LTC4), thromboxanes (TXA2 and TXB2), and prostaglandins (PGDg); cytokines: platelet-activating factor (PAF), bradykinins, interleukins (IL-4, IL-5, IL-6), and tumor necrosis factor-alpha (tnf)
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Adipose cell Brown adipose tissue: mesenchymal derivatives;
specialized for lipid storage; smaller than white adipocytes; has many small droplets; contain many mitochondria. White adipose tissue: mesenchymal derivatives; specialized for lipid storage; diameter varies from 50 to 150 nm; contains a single large lipid droplet; displaces the nucleus; cytoplasm to the cell periphery; near the nucleus contains a Golgi complex, mitochondria, a small amount of rouph endoplasmic reticulum, and free ribosomes; in the thin rim contains smooth endoplasmic reticulum and pinocytotic vesicles.
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PERICYTES is developed from undifferentiated mesenchymal cells;
partly surround the endothelial cells; is surrounded by their own basal lamina; combine characteristics of smooth muscle cells and endothelial cells; under certain conditions, they may differentiate into other cells.
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PLASMA CELL differentiate from antigen-stimulated В lymphocytes;
producers of circulating antibodies; large and ovoid; eccentric nucleus and abundant rouph endoplasmic reticulum; containing a well-developed Golgi complex and centrioles; characteristic "clock face" nucleus results from a large, central nucleolus and large heterochromatin clumps regularly spaced around the nuclear envelope's inner surface envelope.
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Components of extracellular matrix
Fibers: collagen; reticular; elastic; Ground substance: proteoglycans - consist of a core protein to which glycosaminoglycans (GAGs) are attached; glycosaminoglycans (GAGs) - are much smaller than proteoglycans; are straight-chain polymers of repeating amino-glucose heterodimers made up of a hexosamine (glucosamine or galactosamine) and a uronic acid (glucuronic or iduronic acid).
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Dense regular connective tissue
The fibers are tightly packed into parallel bundles; Between the bundles are a few fibroblasts; Small amount of ground substance; Function: transmits the force of muscle contraction, attaches bones, and protects other tissues and organs; Localization: Tendons, ligaments, periosteum, perichondrium, deep fascia, and organ capsules.
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Dense irregular connective tissue
Seems poorly organized than dense regular; Function: Covers tissues and organs, protecting them from multidirectional mechanical stresses; Localization: reticular layer of the dermis and in most organ capsules.
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Adipose tissue Brown adipose tissue:
White adipose tissue: is present in most of the fatty tissue of the body; is characterized by containing unilocular adipose cells; Functions: energy storage, insulation of heat, supportive pads of fat for other organs and gives the body its characteristic contour . Brown adipose tissue: is present in few sites in the body: mediastinum, perinephric fat and around the aorta; contains multilocular adipose cells; Functions: thermoregulation.
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Mucoid connective tissue
mucoid amorphous component of the intercellular substance is dominating, with mucoid cells and some few collagenous fibers; Localization: Wharton’s jelly of the umbilical cord, and bulb of the tooth.
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Pigmented connective tissue
pigment cells are dominating; Localization: It can be seen in the uveal tract of the eye ball (the choroid, the ciliary body and iris).
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