Connective tissue 1 C T Composition Intercellular substance

Connective tissue 1

C. T. Composition Intercellular substance C. T. Cells Fixed Cells C. T. fibers: Collagen, elastic, reticular Fibers Transient Cells Fibroblast: Produce C. T. fibers & intercellular ground substance. Form scare tissue for healing of wounds. Ground substance: Plasma cell : arises from lymphocytes that migrates into C. T. , secretes antibodies. Macrophage or histiocyte: Motile phagocytic cells. Cleans up cellular debris, foreign matter & bacteria. Leukocytes: Adipose (fat) cell : Stores fat as a source of energy. Migrate into C. T. , to defend against bacterial invasion. Lymphocytes Neutrophils Eosinophils Basophils Monocytes Macrophages Pericyte: Surround endothelium of blood capillaries. Under certain conditions, they may differentiate into other cells Mast cell : Releases histamine in allergy & located close to blood vessels of skin , digestive & respiratory systems. Discussed in practical 2 / 13 hydrated amorphous material, formed of - glycosaminoglycans, - protoglycans and - adhesive glycoproteins: 1) Laminin in basal lamina 2) fibronectin in ECM

A) Connective Tissue Fibers: 1) Collagen Fibers - Tough, thick, don’t branch & form bundles - The most abundant fibers - Formed of collagen protein (tropocollagen) fibroblast Collagen - Non –elastic - White in nature - Location: - in Tendon & Dermis Collagen • There at least 15 different fiber type Light microscopic picture 3 / 13 Scanning electron micrograph

2) Elastic fiber - Thin & Branched. - Formed of elastin protein - Elastic fibers are synthesized by fibroblast. - Are consists of Microfibrils surround the amorphous elastin. - Slightly elastic, when stretched, return to its original size. - location: • Elastic membranes (arteries) • In lung (stretched organs) 4 / 13

• Reticular Fibers: Structure: - - They are thin and highly branched. They form heavy delicate network They are formed of collagen & glycoprotein Location: • Framework of lymph nodes & liver

Collagen fibers Elastic fibers Reticular fibers Formed of: Collagen Protein Elastin protein Reticulin protein Characters Tough, thick and don’t branch Thin and branched Location Tendon & Dermis Arteries& lung Framework of lymph nodes & liver Thin and highly branched

B) Connective Tissue Cells: 1 - Fibroblast: • The most abundant cell type in the connec tive tissue. • Are responsible for the synthesis of almost all of the extracellular matrix. • Are elongated, fusiform cells possessing pale staining cytoplasm. • Contain darker stained, large, ovoid nucleus containing a well defined nucleolus. Electron-micrograph fibroblas t Collagen fibers Nucleus reveals a prominent Golgi apparatus and abundant rough endoplasmic RER reticulum (RER). 7 / 13

2 - Adipocytes (Fat cells) Are fully differentiated cells that function in synthesis, storage and release of Fat • Adipogenesis: Multilocular fat cell Mesenchymal cell Brown adipose tissue (primary fat formation in fetus) Blood vessels Unilocular fat cell 8 / 13 White adipose tissue (secondary fat formation in adult)

3 - Mast cell • Originate in bone marrow from mesenchymal cells • In connective tissue, they proliferate and accumulate cytoplasmic granules • Non- activated mast cells contain abundant granules storing histamine, heparin and chemotactic mediators to attract monocyte Mast cell with granules filling the cytoplasm • After activation (binding of a specific antigen to two adjacent Ig. E receptors) mast cell release: - Histamine - Heparin - Tumor necrosis Factor - Interleukins 9 / 13 Electron-micrograph of mast cell

4 - Plasma cell: • • Are oval in shape Derived from B lymphocyte Manufacture antibodies Present in large number in Chronic inflammation • Characterized by: - Cartwheel nucleus eccentric located - Well –developed RER & Golgiapparatus G Cartwheel nucleus RER 10 / 13

5 - Macrophage: • Originates from monocyte, cells formed in bone marrow • Motile cells migrate to the site of inflammation Lysosomes Phagocytic vacuole • Characters: - Abundant lysosomes - Numerous phagocytic vesicles or phagosome - Nucleus has irregular outline Examples: - Kupffer cells in liver. - Microglial cells in CNS. - Osteoclast in bone Large Irregular nucleus 11 / 13