Connective Tissue

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Connective Tissue
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Connective Tissue

• Forms fascias, capsules, sheaths, septa,
  tendons, ligaments, basement membranes, bone,
  blood, cartilage.
• Functions
• a) connection and support
• b) Mononuclear Phagocytic System (MPS)
• c) temperature control
• d) nutrient distribution
• e) tissue repair, etc.

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Anatomical Characteristics

• small number of total cells in tissues
• several different cell types.
• predominance of matrix and fibers

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Fibers

• 1) Collagenous (White) - most common, appear
  white in the living state, composed of 28 types.
• Collagen makes up approx. 25 of the protein
  which is approx. 20-25 of human body weight.
• very inelastic, resists stretching
• Fibers 1 - 100 mm thick, most 1-10.
• Fibrils 0.5 mm thick
• Proto fibrils 10 100 nm

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Collagen Fibers (100,000X)
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secreted by fibroblasts
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Collagen

• Congeals forming gelatin, digested by pepsin.
• Increases in quantity and distribution with age.
• Too little (e.g. Vitamin C Deficiency) scurvy.
• Too much arthritis several other disorders.
• Fibers occur in ligaments, tendons, skin, gel
  forms in many matrices.
• Types I, II, III, V, and XI form fibrils
• Others are non-fibroid, forms of ground substance
  and bind collagen fibers, may be secreted by some
  epithelia.
• Type IV forms meshwork- basal lamina

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Fibers

• Reticular Fibers- Collagen Type III, variant of
  white fiber, but very thin 0.5 to 2 mm
• Fibril diameter with cross striations every
• 64 nm
• Branches more than white fibers
• Strongly argyrophilic.
• Resists stretching.

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Reticular Fibers- Adrenal Cortex
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Fibers

• Elastic (Yellow) - larger than white, no
  striations.
• Some branching contains the protein elastin.
• Yellow and refractive when alive stretches 1.5 x
  its resting length
• Only 1/10 as strong as white.
• Usually occurs with white fibers.
• Secreted by fibroblasts and maybe by smooth
  muscle cells

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Fibers

• Pure elastic CT organs are the ligamentum flava,
  suspensory ligament of the penis in humans, and
  the ligamentum nuchae (neck ligament) of the ox.
• Fibers exhibit poor organization with spaces
  between
• Stain selectively purple with orcein

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Matrix (Ground Substance)

• Glycosaminoglycans (GAG)
• - repeated disaccharide units, one of which is a
  
• sulfated hexosamine. Unique example is
  hyaluronic acid which is a non-sulfated GAG.
• - Chondroitin SO4 (Collagen Type II)
• - Dermatan SO4 (Type I)
• - Keratan SO4 (no collagen),
• - Heparan SO4 (Type III, IV).
• Proteoglycans (PG) GAG chains bound to a
  protein core. Matrix of cartilage.

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Proteoglycan
Glycoprotein
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Connective Tissue Cells

• Fixed and wandering (mobile)
• All derived ultimately from embryonic mesenchyme

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Fibroblasts

• Fixed cells, secrete fibers and matrix
• Closely resemble mesenchyme cells many Golgi
  many cytoplasmic processes 1-2 nucleoli a
  large, light staining nucleus
• May be pleuropotential decrease in number with
  age the most common CT cell.
• Fibrocyte less metabolically active. Mature
  cells of tendons and ligaments.
• Myofibroblasts - modified fibroblasts wound
  repair and maybe some fiber secretion

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Macrophages

• Originate from monocytes and/or hematopoetic stem
  cells
• Main phagocytic cell of CT
• - small, elongate, dark staining nucleus
• - cells sedentary or nomadic cosmopolitan
• - immunologic, antigen presenting cell (form
  MHC)
• Special Names in certain regions
• Kupffer cells in the liver
• Microglial Cells in CNS
• Langerhans Cell in Skin

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Mast Cell

• Smaller cells (compared with macrophage) with
  metachromatic cytoplasmic granules
• Contain heparin (anticoagulant, prevents
  hyaluronidase depolymerization of matrix)
  histamine (capillary permeability, allergic
  anaphylaxis).
• Concentrated around capillaries.
• Functions primary mediator of the inflammatory
  response. non-specific defense reaction
• Can produce hypersensitivity (allergic reaction)

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Mast Cell Activation Degranulation
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Adipocyte

• Adipose (fat) tissue
• Normally 15-20 bw
• Unilocular yellow
• Multilocular - brown

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