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• Connective Tissue is derived from both Hematopoietic and Mesenchymal stem cells
• Connective Tissue Proper Components:

  • Cells:
  • Fixed: Fibroblast, adipose, macrophage, mast cells
  • Transient: lymphocytes, plasma cells and other leukocytes
  • Fibroblasts (most abundant) produce matrix
  • Protein fibers (loose or densely arranged):
  • Collagen (type I) - most common
  • Collagen type III (Reticular)
  • Elastic
  • Collagen type II is only in cartilage
  • Ground substance: gel-like
  • Variable blood supply
• PLASMA CELL:

  • Derived from B-lymphocytes
  • Function: production of antibodies
• MAST CELL:

  • Functions: produce chemical mediators of inflammation (pain, edema, allergic reactions) via production of heparin, histamine, prostaglandins and leukotrienes
• Ground substance in Connective Tissue Proper contains proteoglycans (proteins and glycosaminoglycans - hyaluronic acid)
• Example of CT Proper: Areolar Tissue, Adipose Tissue, Reticular Tissue (Type III collagen fibers - reticular)
• Reticular fibers are collagen type III and produced by fibroblast cells

  • Found mostly in hemopoietic organs (red bone marrow) and lymphatic tissues (spleen, lymph nodes) and arteries
• Elastic Tissue:

  • Elastic Fibers:
  • Produced by fibroblasts
  • Composed of elastin and fibrillin microfibrils
• Dense Regular Connective Tissue:

  • Composed of densely packed collagen (type I) bundles and oriented into parallel arrays of fibers and cells
  • Few fibroblasts and sparse ground substance
  • Found in tendons, aponeuroses, and ligaments
• Dense Irregular Connective Tissue:

  • Abundance of fibers (mostly collagen type I)
  • Few fibroblasts
  • Little ground substance
  • Fibers arranged in bundles and oriented in various directions
  • Found in the dermis of skin and submucosa of intestines
• Cartilage:

  • Chondrocytes in lacunae within a firm gel-like ground substance of chondroitin sulfate
  • Avascular
  • Covered by a fibrous perichondrium
  • Ground substance: Type II collagen, elastin, proteoglycans (proteins and glycosaminoglycans - chondroitin sulfate)
  • Three types of cartilage: Hyaline cartilage, Elastic cartilage, Fibrocartilage
• Bone:

  • Matrix (hardened):
  • Inorganic: Calcium salts
  • Organic (osteoid): Type I collagen, Proteoglycans
  • Stem cell: osteoprogenitor
  • Synthesis: osteoblasts
  • Maintenance: osteocytes
  • Dissolution: osteoclasts (hematopoietic)
  • Spongy Bone, Compact Bone
• Osteocytes in lacunae of interstitial fluid within a calcified matrix

  • Matrix comprised of osteoid & calcium salts (mainly Ca3(PO4)2 - hydroxyapatite)
  • Well vascularized