histo connective tissue

• Connective tissue


  One of the basic tissues which gives structural and metabolic support to the organ and other tissue of the body. It connects other tissues.
• Functions of connective tissue

  • Support
  • Structural & Mechanical
  • Packing
  • Storage
  • Transport
  • Repair
  • Defense
• Connective tissue


  • Cells
  • Matrix
• Components of extracellular matrix

  • Fibers
  • Ground substance
• Cells of connective tissue

  • Fixed cells (fibroblast, fibrocytes, mesenchymal cells, adipocyte, fixed macrophages)
  • Free cells (free macrophage, mast cell, plasma cells, leucocytes)
• Fibroblast


  Most commonly seen, fusiform with slender cytoplasmic process, large oval nucleus, responsible for fiber production, old cells are fibrocyte, contractile cells are myofibroblast
• Adipocytes


  Store lipid, appears as empty space, incapable of division, aggregate in adipose tissue with reticular fibre
• Mesenchymal cells


  Undifferentiated cells, stellate in shape with cytoplasmic process, pluripotent cell, near blood vessels as adventitial cell
• Macrophages (histiocytes)


  Free and fixed type, fixed cells have irregular shape with filopodia process and dark indented eccentric nucleus, derived from monocyte, involved in phagocytosis, fused to form giant cell, free cells are rounded with no filopodia
• Plasma cells


  Oval basophilic cells with eccentric nucleus and heterochromatin as cartwheel nucleus, derived from B lymphocyte, produces immunoglobulin, antibody collected as Russell body, present in respiratory tract and gastrointestinal tract
• Mast cell


  Round or fusiform shaped, mostly along blood vessels, metachromatic granules in cytoplasm containing histamine or heparin, look like basophil so called as connective tissue basophil, connective tissue mast cell have heparin granule and present in skin, mucosal mast cell are small and present in lamina propria of GIT and respiratory tract
• Leucocytes


  • Granulocytes (neutrophils, eosinophils, basophils)
  • Agranulocytes (lymphocytes, monocytes)
• Collagen fibre


  White colour when fresh, do not branch, wavy, present in bundle, composed of collagen protein, fibres composed of fibrils made of microfibrils, microfibrils made up of tropocollagen with striations, synthesized by fibroblast
• Tropocollagen


  Synthesized by fibroblasts and released into extracellular space where they get polymerized to form collagen fibrils, collagen on boiling gives gelatin, more than 25 types are present, also synthesized by chondroblasts, osteoblasts, smooth muscle, and odontoblasts
• Types of collagen


  • Type 1 (bones, tendons, dermis etc)
  • Type 2 (cartilage)
  • Type 3 (reticular fibres)
  • Type 4 (basement membrane)
  • Type 5 (blood vessels)
• Collagen synthesis


  1. Amino acids

  2. Procollagen

  3. Three chains

  4. Tropocollagen

  5. Collagen
• Elastic fibre


  Yellow in color when fresh, composed of elastin protein, singly present, branched and anastomose forming a network, can be stretched (one and a half times), synthesized by fibroblast and smooth muscle cells in blood vessels, found in ligamentum flava, ligamentum nuchae, large arteries
• Reticular fibre


  Structurally similar to collagen fibres, very thin immature collagen fibre, actively branch to form delicate network therefore named Reticular, form supportive framework of lymphoid tissue, stained black by silver salts (argyrophillic), composed of Collagen Type III
• Ground substance


  Transparent & homogeneous, fills spaces between cells and fibres, acts as molecular sieve facilitating diffusion between blood and tissues, composition: mucopolysaccharides, structural glycoproteins, water & electrolytes
• Components of ground substance

  • Mucopolysaccharides (glycosaminoglycans - hyaluronic acid, heparan sulphate)
  • Structural glycoproteins (fibronectin, chondronectin, laminin)
  • Water & electrolytes
• Classification of connective tissue

  • Ordinary connective tissue (loose, dense regular, dense irregular)
  • Connective tissue with special properties (adipose, mucoid, reticular, pigmented)
  • Scleral connective tissue (bone, cartilage)
  • Lymphoid and haemopoietic connective tissue
• Loose connective tissue


  • Subperitoneal tissue, endomysium, lamina propria
• Dense regular connective tissue


  • Tendon, ligament, aponeurosis
• Dense irregular connective tissue


  • Dermis of skin
• Connective tissue with special properties

  • Elastic - ligamentum nuchae

  Mucoid/Embryonic - Wharton's jelly

  Reticular - stroma of lymphoid organ

  Adipose - adipose tissue
• function of •Fixed Cells: Production & Maintenance of Extracellular Matrix.
• function of •Free Cells:Tissue reaction to injury or invasion of Microorganisms.