Connective Tissue

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Connective Tissue

• Dr. Ashraf Hussain

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Connective Tissue

• These tissues connect and support other tissues
  of the body

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Connective Tissue

• Mechanical support
• Medium for exchange of nutrients waste products
• Energy store and thermal insulation
• Defensive functions
• a) Barrier b) Engulf bacteria
• c) Antibodies
  

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Connective tissue

• Connective tissue comprises a diverse group of
  cells embedded in a tissue-specific extracellular
  matrix
• Different type of connective tissue are
  responsible for a variety of functions
• Classification of connective tissue is based on
  the composition and organization of its cellular
  extracellular components and on its functions

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Structure of connective tissue

• Cells
• Intercellular substance or matrix

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Matrix

• Amorphous ground substance
• Thread like formed elements called fibers
  (collagen fibers, reticular fibers, elastic
  fibers)
• Tissue fluid

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Cellular component interspersed in intercellular
substance different kinds of cells Fibers
part of the formed substance of C.T. embedded
in ground substance Matrix ground substance
fibers
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Connective tissue cells

• Resident cell population
• Fibroblasts
• Macrophages
• Adipose cells
• Mast cells
• Undifferentiated mesenchymal cells

• Wondering cell population
• Lymphocytes
• Plasma cells
• Neutrophils
• Eosinophils
• Basophils
• Monocytes

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Leucocytes in loose supporting tissueF-Fibroblast
s, Er-Erythrocytes, N-Neurtrophils,
Eo-Eosinophils, L-lymphocytes, P-Plasma cells,
M-Macrophages
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Connective tissue cells

• Fibroblasts
• Histiocytes (Macrophages)
• Plasma cells
• Mast cells
• Fat cells

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ADULT CONNECTIVE TISSUE COMPONENTS Connective
Tissue Cells
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Connective tissue cells

• Fibroblasts
• Most abundant
• Appearance varies in relation to functional state
• Produce connective tissue fibers secrete ground
  substance

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Mature Fibroblasts
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Active fibroblasts
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Histiocytes (Macrophages)

• Abundant
• Inactive and active histiocytes
• Scavenger cells
• Foreign body giant cells
• Antigen presenting cells

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Macrophage
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Plasma cells

• Generally rare but numerous at certain sites
  e.g., intestinal mucosa, lymphoid organs
• Nucleuscart wheel appearance
• Production of antibodies

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Mast cells

• Mast well fed (German)
• Abundant in loose connective tissue around blood
  vessels
• Secrete Heparin ( anticoagulant)
• Histamine (vasodilator)

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Mast Cells
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Fat cells (adipocytes)

• Form adipose tissue when accumulate together
• Signet ring appearance

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• Blue dotted lines - Adipocytes
• Orange Arrows - Fat droplet "space"
• Green Arrow - Nuclei of Adipocyte

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Connective tissue fibers

• Long slender protein polymers which are found in
  differing proportions in various types of
  connective tissue
• Predominant fiber type is responsible for
  conferring specific properties to the tissue

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Connective tissue fibers

• Collagen fibers --collagen
• Reticular fibers --collagen
• Elastic fiber -------elastin

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Collagen

• Long moleculetropocollagen
• Three polypeptide chains intertwined together
  triple helix
• By now 19 varieties of collagen have been
  identified
• Most important best studied are I,II, III, IV
  V.

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Growth of molecular character of a collagen fibril
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Collegen fibers are most abundant type of
connective tissue fibers

• Collagen fiber formation involves events that
  occur both within and outside the fibroblast

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Collagen fibers

• Diameter (2-10 micrometer)
• Run randomly in various directions
• In many parts, collagen fibers lie parallel to
  each other forming bundles of various sizes
• Flexible but inelastic (non-extensible)
• Pink colour with HE stain

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Blue arrow - Collagen BundleGreen Arrow -
Fibroblast nuclei
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Reticular fibers

• Reticular fibers provide a supporting framework
  for the cellular constituents of various tissues
  and organs
• Reticular fibers are named for their arrangement
  in a mesh-like pattern or network

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Reticular fibers

• Very thin branching fibers (retenet)
• Diameter (0.5 to 2 micrometer)
• Coating of proteoglycans glycoproteins black
  colour with silver staining, red with PAS
• Abundant in connective tissue around muscle
  fibers, nerve fibers, acini of glands, lymphoid
  organs bone marrow

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Elastic fibers

• Highly elastic can stretch one and half time
  their original length
• Diameter (0.2 to 1.0 mic.m)
• Branch rejoin to form loose network
• Found in lungs, large arteries, ligamenta flava
  (connecting laminae of successive vertebrae)

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Elastin fibres
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Ground substance

• Ground substace occupies the space between the
  cells and fibers
• Ground substance consists largely of
  proteoglycans and hyaluronic acid
• Proteoglycans and Glycosaminoglycans (GAG) are
  responsible for the physical properties of ground
  substance

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Embryonic connective tissue

• Develops from mesoderm is known as Mesenchyme
• Composed of star-shaped cells which lie in an
  abundant relatively homogeneous intercellular
  substance
• Mucous tissue Whartons jelly

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Arrows cells in mitosis C small blood
vessels Ground substance devoid of fibers Cell
processes extend into homogeneous ground substance
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Disorders of connective tissue

• Marfan syndrome - a genetic disease causing
  abnormal fibrillin
• Scurvy - dietary deficiency in Vit.C leading to
  abnormal collagen.
• Ehlers-danlos syndrome - a genetic disease
  causing progressive deterioration of collagens
  affecting different sites in the body such as
  joints, heart valves arterial walls

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Disorders of connective tissue

• Osteogenesis imperfecta ( brittle bone disease)
  insufficient production of good quality collagen
  to produce healthy, strong bones
• Spontaneous pneumothorax collapsed lungs,
  believed to be related to subtle abnormalities in
  connective tissue

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