1. DEVELOPMENT OF CONNECTIVE TISSUE Mesenchyme Loose Connective Tissue Mesenchymal Cells Fibroblasts Fibers

2. Cell Lineage from Mesenchymal Cells

3. TYPES OF CONNECTIVE TISSUE Loose Connective Tissue Dense Irregular Connective Tissue Dense Regular Connective Tissue (e.i. mesentery, omentum) (e.i. dermis of skin) (e.i. tendons, ligaments, cornea)

4. DENSE IRREGULAR CONNECTIVE TISSUE (DERMIS OF SKIN)

5. DENSE REGULAR CONNECTIVE TISSUE Tendon (longitudinal Section) Tendon (tranverse Section)

6. ELASTIC CONNECTIVE TISSUE IN BLOOD VESSEL WALL Internal elastic lamina

7. CONNECTIVE TISSUE FIBERS Collagenous Fibers (bundles) Reticular Fibers (networks) Elastic Fibers (anastomosing bundles)

8. RETICULAR CONNECTIVE TISSUE reticular fibers (argyrophilic)

9. COLLAGEN FIBER BUNDLE Fiber Fibril Microfibril Periodic Bands Tropocollagen alpha 1 peptide alpha 2 peptide TEM of Collagen Fibers SEM of Collagen Fibers

10. SCANNING EM OF COLLAGEN FIBER BUNDLES

11. procollagen tropocollagen ground substance (mucopolysaccharide) RER TEM of Fibroblast and Collagen Bundles Collagen Types I - skin, bone, tendon cornea (most common type) II- cartilage, embryonic cornea III- reticular fibers, loose c.t., blood vessel walls, dermis IV- basal lamina of epithelium (no fibers, mat of randomly-oriented molecules) FIBROBLAST collagen fiber bundles

12. TEM OF FIBROBLAST WITH COLLAGEN BUNDLES

13. FIXED CONNECTIVE TISSUE CELL TYPES Fibroblast (fiber producing cell) Fibrocyte (mesenchymal- pluropotent) Adipocytes (fat storage) Fixed Macrophage (histiocyte)

14. Adipocytes fibroblast Macrophage (light micrograph) TEM of Macrophage Fixed Connective Tissue Cells

15. MONONUCLEAR PHAGOCYTIC SYSTEM Mononuclear wandering cell coalescence Giant Cell MacrophagesOsteoclastsKupffer Cells Microglial Cells Sinusoidal Endothelia lymph nodes bone marrow connective tissue lung serous cavities spleen bone resorption liver sinusoids central nervous system liver spleen marrow Monocyte (reticuloendothelial system) ( all characterized by phagocytic activity)

16. LYMPHOCYTES AND PLASMA CELLS (Agents of the immune response) differentiation stimulated by immune activation LymphocytesPlasma Cells (produce immunoglobulins -antibodies)

17. EOSINOPHILESMAST CELLS actively phagocytic destroy immune complexes (antigen-antibody) Secretion Products: 1. Slow-reaction substance of anaphalaxis 2. Heparin- anticoagulant 3. Histamine- stimulates inflammation 4. Serotonin- vasoconstrictor 5. Eosinophil Chemotactic Factor

18. Connective Tissue Cells Macrophage Plasma Cell Lymphocyte

19. TRANSMISSION EM OF AN EOSINOPHILE

20. TRANSMISSION EM OF A MAST CELL