Connective Tissues

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CONNECTIVE TISSUE
•         Development of connective tissue
-Connective tissue develops from mesenchyme, a derivative of mesoderm.
-To a large extent, connective tissue consists of the nonliving intercellular substances produced by certain of its cells.
-Cartilage & bone, as well as ligaments, tendons & fasciae develop from mesenchyme & represent types of connective tissue that consist chiefly of intercellular substances.
•         Connective tissue groups
  1. Loose connective tissue,
  2. Adipose tissue (fat tissue),
  3. Blood cells,
  4. The blood cell forming tissues,
  5. Dense connective tissue,
  6. Cartilage &
  7. Bone
•         Basic components of general connective tissue
  1. Cells
  2. Ground substance
  3. Fibers
•         Cells in general connective tissue
  1. Cells that are intrinsic components of connective tissue:
      1. Fibroblasts,
      2. Undifferentiated mesenchymal cells,
      3. Pigment cells &
      4. Fat cells (Adipocytes)
  2. Cells that belong to the immune system:
      1. Macrophage cells (or histocytes),
      2. Mast cells,
      3. Lymphocytes,
      4. Plasma cells,
      5. Monocytes &
      6. Eosinophils
•         Cells of connective tissue
•         Connective Tissue
•         Fibers of connective tissue
  1. Collagen fibers:
    1. Type I: connective tissue, tendons, ligaments, fascia, aponeuroses, dermis of skin & in meninges.
    2. Type II: hyaline cartilage
    3. Type III: reticular fibers
    4. Type IV: basal lamina of basement membranes, lense capsule.
  2. Reticular fibers:
    1. Collagen fiber type III
  3. Elastic fibers:
    1. Ligamentum nuchae, Ligamenta flava
•         Three types of arrangement of collagen fibers in: (A) dense irregular connective tissue; (B) a ligament; (C) a tendon.
•         Loose connective tissue in the mesentery, viewed as a whole mount preparation stained to show the interwoven collagen fibres (red) and network of thin elastic fibres, with interspersed cells. Van Gieson/ Verhoeff’s stain.
•         T. S. of a tendon showing fibrocytes enclosed between bundles of collagen fibres.
•         Connective tissue
Ø  Intercellular substances or matrix:
Ø  Ground substance:
Ø  Biochemically complex & highly hydrated semisolid gel.
Ø  Glycosaminoglycans.
Ø  Numerous blood capillaries & lymphatic capillaries.
Ø  Decreases with age.
Ø  Classification of connective tissue
•         Types
  1. Ordinary connective tissue:
    1. Irregular connective tissue:
      1. Loose connective tissue
      2. Dense irregular connective tissue
      3. Adipose tissue
    2. Regular connective tissue
            Fasciae, ligaments, tendons & aponeurosis
  1. Special connective tissue:
    1. Mucoid tissue
    2. Pigmented connective tissue
    3. Bone &
    4. cartilage
•         Types
  1. Areolar tissue
  2. Adipose tissue
  3. White fibrous tissue
  4. Elastic tissue
  5. Reticular tissue
  6. Mucoid tissue
  7. Areolar tissue:
Distribution:
  • Subcutaneous tissue where fat is absent: eye lid, scrotum, penis.
  • Submucous coat of alimentary tract
  • Subserous coat
  • Interior of the viscera
2. Adipose tissue:
Distribution:
  • Subcutaneous tissue as panniculus adiposus
  • Around the kidney, in the mesenteries & omenta.
  • In the bone marrow & as localized fat in synovial membrane.
3. White fibrous tissue:
Distribution:
  • Ligaments
  • Tendons
  • Fascial sheaths
4. Elastic tissue:
Distribution:
    • Ligamenta flva,
    • Vocal folds & crico-vocal membrane,
    • Mucous membrane of trachea, bronchi & lung alveoli,
    • Coats of larger blood vessels.
5. Reticular tissue:
Distribution:
    • Lymph nodes, spleen, liver, kidneys, lungs, bone marrow etc.
6. Mucoid tissue:
Distribution:
    • Wharton’s jelly of the umbilical cord,
    • Pulp of developing teeth,
    • Vitreous body of eye ball.
•         Loose connective tissue
•         Fibrous tissue
  1. Regular fibrous tissue or regular connective tissue: tendons, deep fascia, intermuscular septa, aponeuroses, central tendon of diaphragm, fibrous pericardium & dura mater.
  2. Dense irregular tissue: dermis, connective tissue sheaths of muscles & nerves, capsules of glands, sclera, periosteum & adventitia of blood vessels.
•         Dense irregular connective tissue
•         Dense irregular & loose Connective Tissue
•         Dense Irregular Connective Tissue & Adipose Tissue
•         Dense regular connective tissue (L.S.)
•         L. S. through a tendon, showing the parallel organization of its collagen fibres. A few long, flattened Fibrocyte nuclei are also visible
•         Tendon L.S.
•         Dense regular connective tissue (T.S.)
Elastic tissue:
Ø  Bulk of connective tissue is formed by elastic fibers.
Ø  E.g. ligamentum flava, vocal ligaments of larynx.
Reticular tissue:
Ø  Made up of reticular fibers.
Ø  E. g. lymph nodes, glands, bone marrow, spleen.
•         Embryonic connective tissue
•         A section of fetal mesenchyme showing mucoid tissue sparsely populated with cells
•         Adipose Tissue
Structure:
Ø  An aggregation of fat cells, also called adipocytes.
Ø  Each fat cell contains a large droplet of fat that fills it.
Ø  Cytoplasm of the cell forms a thin layer just deep to the plasma membrane
Ø  Nucleus is pushed against the plasma membrane & is flattened.
•         Adipose Tissue
Distribution:
Ø  In superficial fascia over most of the body- panniculus adiposus, except superficial fascia of eyelids, scrotum & penis.
Ø  Fills several hollow spaces in the body, e. g. orbits, axilla & ischiorectal fossae. In adult much of the space in marrow cavities of long bones is filled by fat in the form of yellow bone marrow.
Ø  Around abdominal organs, specially the kidneys (perinephric fat).
Ø  In greater omentum & in other peritoneal folds.
•         Adipose tissue in intestine
•         EDEMA
Other causes:
  1. Venous return may become impaired.
  2. Lymphatics may become obstructed.
  3. Permeability of capillaries may be increased.

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