Connective Tissue Dentistry PDF

Connective tissue DR.Amy Diab ▪ Origin: mesoderm ▪ Characteristics:. Formed of Widely separated cells with large amount of ground substance (matrix).. Penetrated by Blood vessels, nerves and lymphatic vessels.. Connects, supports and protects other tissues e.g epithelium & organs ...

Connective tissue DR.Amy Diab ▪ Origin: mesoderm ▪ Characteristics:. Formed of Widely separated cells with large amount of ground substance (matrix).. Penetrated by Blood vessels, nerves and lymphatic vessels.. Connects, supports and protects other tissues e.g epithelium & organs  Connective tissue Ground Cells Fibers substance soft → Fixed cells ( stable, long lived cells) Collagen connective tissue proper Free cells (short lived cells Rubbery & firm that enter the connective tissues from blood) Elastic → cartilage Reticular solid→ bone Fluid→blood Connective Tissue Proper Connective Tissue Cells: 1)Fixed Cells: stable population, long lived cells, produced in C.T. and remain in it. 2)Free Cells: changeable population, motile cells, belong to immune system, entering C.T. from blood, short lived and wander through C.T.  A- Fixed C.T. Cells 1) Undifferentiated Mesenchymal cells In embryo: Stem cells, able to differentiate into other C.T. cells. In adult: Remain undifferentiated in certain areas, act as stem cells pericytes and bone marrow cells. ❖ Small irregular branched cells. ❖ Pale basophilic cytoplasm with central large oval pale nucleus & nucleoli. ❖ Few organelles (many ribosomes).  Function: 1) In embryo: Act as stem (Mother) Cells; can differentiate into: All types of C.T. cells Smooth muscle cells Endothelial cells. 2) In adult: they remain undifferentiated in certain areas to act as life-long source for some cells e.g. a) in bone marrow→ Blood cells b) around blood vessels→ Pericytes  A- Fixed C.T. Cells 2) Pericytes: ▪UMC of adult. ▪Present around blood capillaries ▪LM: Branched with oval nucleus & pale cytoplasm. ▪Give fibroblasts & smooth muscles throughout life. ▪Vasoconstriction  Function of pericytes = UMCs of the adult - During injury of C.T. & blood vessels, they can differentiate into: Fibroblasts Smooth muscle cells Endothelial cells - Pericytes can contract & constrict blood vessels  A- Fixed C.T. Cells 3) Fibroblasts: Most common type, in all C.T. proper Origin: UCMs and pericytes Flat elongated cell with processes. LM & EM picture of protein forming cell  3) Fibroblasts: Function: 1-Formation of C.T. fibers (secret its protein) and matrix (build C.T.) 2- Repair of C.T. after injury.  A- Fixed C.T. Cells 4) Fibrocytes: -Old inactive fibroblasts -Smaller, few processes -Less basophilic cytoplasm with less rER & dark nucleus Function: Continuous slow turn over of C.T. fibers & matrix (maintenance of C.T.)  A- Fixed C.T. Cells 4) Fat cells (adipocytes): A)Unilocuolar (White) Fat Cells: Large oval cell with peripheral flattened nucleus Cytoplasm: thin film around large fat globule Unilocuolar (White) Fat Cells: In H&E stain---signet ring appearance Special stain: Sudan III (orange) Function: Storage of fat & heat insulator B) Multilocuolar (Brown) Fat Cells: Small rounded cells with central rounded nucleus Many small fat droplets, many mitochondria which contain cytochrome pigment cause brown color. Less common Heat generation Multilocuolar (Brown) Fat Cells:  A- Fixed C.T. Cells 5) Fixed Macrophage (histiocyte): Derived from monocytes. Attached to C.T. fibers and scattered along them, mainly collagen fibers (Fixed). Large branched cell with pseudopodia, so they have variable shape. Nucleus is small dark, oval or kidney shaped with vacuolated cytoplasm Fixed Macrophage (histiocyte): Vital stain (as trypan blue) EM picture: -Irregular surface (Pseudopodia, microvilli). - Large phagocytosed particles - Lysosomes (1ry & 2ry) - Few rER, prominent golgi Fixed Macrophage (histiocyte) Functions: - Phagocytosis - Clean wounds Fuse with each other form Giant cells to engulf large foreign bodies - Antigen presenting to lymphocyte - Destruction of old RBCs(liver& spleen  A- Fixed C.T. Cells 6) Reticular Cells: origin UMCs - Present in the stroma of the organs - Small branched with long processes - Silver stain can demonstrate them. Functions: 1. Form reticular fibers 2. Act as supporting cells. They form a reticular network with reticular fibers 3. Can act as phagocytic cells, on need.  B- Free C.T. Cells 1) Plasma Cells: Origin: B-lymphocyte differentiate to plasmablast then plasma cell LM: oval with eccentric nucleus (cart-wheel or clock-face). Cytoplasm is deep basophilic with -ve Golgi image Plasma Cells: Sites: abundant in lymphoid tissue. rarely found in blood. E M: well-developed Golgi apparatus Closely spaced cisternae of rER & Mitochondria Functions: formation & secretion of antibodies Plasma Cell  B- Free C.T. Cells 2) Mast cells: Origin:UMCs in bone marrow. Sites: around blood vessels and sub-epithelial C.T. (respiratory & digestive systems) LM: Oval cell, eccentric nucleus Basophilic cytoplasm Stain: Metachromatic stain with toluidine blue EM: Well-developed Golgi apparatus Electron-dense granules filling the cytoplasm rER & mitochondria Functions: Secretion of: 1- histamine 2- heparin 3- eosinophil chemtactic factor.  B- Free C.T. Cells 3) Free Macrophages: They are the same as histiocyte. The only difference is they are wandering in the connective tissue. B- Free C.T. Cells 4) Blood Leukocytes: All types migrate from the blood stream to C.T. to perform their defensive functions. Connective Tissue Fibers White Collagen Fibers Synthesis: Mainly fibroblasts + chondroblasts, osteoblasts & odontoblasts LM: Wavy branching bundles, formed of non- branching parallel fibers Staining: Pink in color in H&E (acidophilic) Character: Strong, flexible & not elastic Function: Give strength to tissues & resist stretching Synthesis: Mainly fibroblasts + chondroblasts LM: Thin long branching fibers. Run singly not in bundles. Staining: Pink in H&E, Brown with Orcein. Character: Stretchable Function: Give elasticity to tissues  Reticular Fibers Synthesis: Mainly fibroblasts + reticular cells LM: Very thin fibers that branch & anastomose forming a network Staining: Not seen by H&E, Brown with Silver stain (argyrophilic) Character: Delicate & flexible Function: Form the stroma (background) which supports organs  Types of Connective Tissue Proper Loose C.T. Dense C.T. Reticular Mucoid Adipose Loose Connective Connective Connective (Areolar) Tissue. Tissue. Tissue White Fibrous Yellow elastic Connective connective Tissue. tissue Loose Connective Tissue Proper Loose (Areolar) C.T. Contains all types of C.T. cells (mainly fibroblasts, fat cells & macrophages) and all types of C.T. fibers (mainly collagen), embedded in an abundant matrix. Contains potential cavities (areolae), which can accommodate large amounts of fluids or gases. Present all over the body except the brain. Around organs and blood vessels. Under epithelium; in submucosa & dermis of skin. Functions: It binds tissues together & surrounds organs. Provides support and elasticity to organs and tissues. Reticular C.T. Reticular Fibers: fine branching fibers. Reticular Cells: branched cells with long processes that are connected with each other. Reticular cells and fibers form a network (reticulum) which is stained brown by Silver stain (Ag). Sites & Functions: Form the framework (Stroma) of organs (to support the functioning cells) e.g. lymph node, spleen & liver.  White Adipose C.T. Unilocular fat cells: large with flat peripheral nucleus Each cell contains a large single fat droplet. Fat is not pigmented. Poor blood supply Sites: Under the skin, mammary gland, around the kidney. Functions: Storage of fat. Heat insulator. Support of organs e.g. kidney. Forms the body contours.  Brown adipose Multilocular fat cells: small with central or eccentric rounded nucleus Each cell contains many fat droplets. The fat is pigmented (brown) due to: a) High vascularity b) Cytochrome pigments in mitochondria Site: ◦ Abundant in newborns ◦ limited to certain regions in adults including supraclavicular, interscapular, axillary & thoracic paravertebral regions. Functions: Heat generation Mucoid C.T. Structure: Large amount of jelly-like ground substance rich in mucus and hyaluronic acid. UMCs & fibroblasts that communicate by their processes. Fine collagen fibers. Sites: Umbilical cord (known as Wharton's Jelly). Pulp of growing teeth. Vitreous humor of the eye. Function: Protects near-by structures from pressure. Dense Types of Connective Tissue Proper  Regular White Fibrous C.T. Parallel collagen bundles with fibroblasts in-between. Sites: Tendons, cornea Functions: Withstand stretch in one direction Irregular White Fibrous C.T. Irregularly arranged collagen bundles with fibroblasts in-between. Sites: periosteum perichondrium dermis of skin capsule of organs. Functions: Withstand stretch in different directions Yellow Elastic C.T. Structure: Mainly elastic fibers (so appears yellow in fresh state) and Fibroblasts. Sites: Aorta, bronchi & bronchioles, ligaments. Function: Recoil after stretch.