HISTOOOO (TRANS: Connective tissue)

• General types of connective tissue

  • Embryonic connective tissue
  • Adult connective tissue
• Embryonic connective tissue


  • Mesenchyme
  • Mucous tissue
• Adult connective tissue


  • Ordinary/Connective Tissue Proper
  • Specialized Connective Tissue
• Ordinary/Connective Tissue Proper


  • Loose Connective Tissue
  • Dense Connective Tissue
• Dense Connective Tissue


  • Regular
  • Irregular
• Specialized Connective Tissue


  • Cartilage
  • Bone
  • Blood
  • Hematopoietic tissue
• Components of connective tissue

  • Cells
  • Fibers
  • Ground substance
• Major constituent of connective tissue is the extracellular matrix (ECM)
• Components of extracellular matrix (ECM)


  • Protein fibers (collagen, reticular, and elastic fibers)
  • Ground substance (anionic macromolecules and multiadhesive glycoproteins)
• Functions of connective tissue

  • Support and packaging
  • Storage
  • Transport
  • Defense
  • Repair
• Cell types in connective tissue

  • Fixed cells
  • Wandering or mobile cells
• Mesenchyme


  Embryonic tissue where all types of connective tissues originate

  
• Cells of connective tissue

  • Fibroblast
  • Adipocytes
  • Macrophages and the Mononuclear Phagocyte System
  • Mast Cells
  • Plasma Cells
  • Leukocytes
• Fibroblasts


  Originate locally from undifferentiated mesenchymal cells and spend all their life in connective tissue, synthesize extracellular components
• Adipocytes


  Connective tissue cells specialized for storage of neutral fats or for the production of heat, incapable of mitotic division
• Types of adipose tissue

  • White adipose tissue
  • Brown adipose tissue
• Mast cells, macrophages, and plasma cells originate from hematopoietic stem cells in bone marrow, are transient cells of most connective tissues, usually die by apoptosis
• Macrophages


  Important agents of defense, act as scavengers due to mobility and phagocytic activity, play a fundamental role in the development of immunity
• Activated macrophages


  Macrophages that are stimulated, change their morphological characteristics and metabolism, acquire enhanced phagocytic and digestive capabilities
• Names of macrophages in different organs

  • Kupffer cells (liver)
  • Microglial cells (central nervous system)
  • Langerhans cells (skin)
  • Osteoclasts (bone tissue)
• Mast cells are large, oval or round connective tissue cells, 20-30 μm in diameter, with cytoplasm filled with basophilic secretory granules
• Metachromasia


  Displayed by mast cells due to high content of acidic radicals in their sulfated glycosaminoglycans, which means they can change the color of some basic dyes
• Important molecules released from mast cell granules

  • Heparin
  • Histamine
  • Serine proteases
  • Eosinophil and neutrophil chemotactic factors
  • Leukotrienes C4, D4, and E4 (SRS-A)
• Types of mast cells

  • Perivascular mast cells
  • Mucosal mast cells
• Plasma cells


  Large, ovoid cells with basophilic cytoplasm due to richness in rough ER, have a spherical but eccentrically placed nucleus with a cartwheel appearance, average lifespan of 10-20 days

  
• Diapedesis


  Migration of leukocytes from the blood vessels to the connective tissue, increases greatly during inflammation
• Chemotaxis


  Responsible for the migration of large quantities of specific cell types to regions of inflammation, happens under the influence of chemotactic factors
• Components of the extracellular matrix

  • Fibers (collagen, reticular, elastic)
  • Ground substances (glycosaminoglycans, proteoglycans, multiadhesive glycoproteins)
• Collagen


  The most abundant type of connective tissue fiber, with various types present in different tissues
• Types of collagen


  • Collagen that form fibrils
  • Fibril-associated collagens
  • Collagen that forms anchoring fibrils
  • Collagen that forms networks
• Collagen synthesis


  Activity of fibroblasts, chondroblasts, osteoblasts, and odontoblasts, involves production of procollagen chains that intertwine to form triple helices
• In some collagen types, fibrils associate further with FACIT collagens to form fibers, and collagen type I fibers can form large bundles
• Collagen type IV, present in all basement membranes, assembles as a meshwork that constitutes a major structural component of the basal lamina
• Odontoblasts


  Cells found in the dental pulp
• Odontoblasts, has now been shown to occur in many cell types
• Collagen production


  Refers to the production of the collagen
• Fibroblast


  Cells that produce collagen
• Chondroblast


  Found in cartilage which also produce collagen
• Procollagen chains


  Polypeptides initially formed on ribosomes of the rough ER
• Procollagen chain formation


  Intertwine in ER cisternae to make triple helices