Connective Tissue

• Outline of Connective Tissue

  • General and Histological Characteristics
  • General Functions
  • Embryonic Origin and Development
  • General Composition
• Connective Tissue


  • One of the four fundamental tissues
  • Basic tissue characterized by abundance of extracellular material and paucity of cells
  • Most abundant and most widely distributed
  • Significant to know when it comes to surgery
  • Has 2 classifications: Connective Tissue Proper, Special Types
• Connective tissue has abundance of extracellular material (ground substance and protein fibers) and paucity of cells (few cells)
• Structural Properties of Cells

  • Tensile Strength: Mainly due to presence of collagen fibers, refers to resistance to tension
  • Elasticity: Due to presence of elastic fibers
  • Volume: Due to presence of extracellular material, glycoproteins, and complex carbohydrates
• General Functions of Connective Tissues

  • Support for all other tissues of human body
  • Protection - e.g. specialized cells
  • Transport - e.g. blood
  • Insulation - e.g. adipose tissue
  • Other specialized uses include Hematopoietic, Immunologic, Tissue Repair
• Connective tissue arises from

  The primitive mesenchymal cell/multipotential embryonic mesenchyme cells
• Mesenchymal cells derive from the mesoderm for connective tissues
• Connective tissues have 2 main components: Cells (in smaller/fewer number) and Extracellular Substance (in greater number) including Ground substance and Protein fibers
• Connective tissues have low density due to abundance of fibers and ground substance, and paucity of cells
• Connective tissues


  • Embryonic, mesenchymal type
• Connective tissues


  • Have few cells only and less fibers
• Ground Substance


  • Clear-appearing background; a little bit more fluid
• Fibers


  • Wavy, pinkish, fine, sparse lines
• Cells in connective tissues

  • Dark, distant, and fewer in number relative to the extracellular matrix
• Components of Connective Tissue Proper

  • Collagenous tissue
• Main types of Connective Tissue Proper

  • Collagenous, Elastic tissue
• Overview of Collagenous Tissue

  1. Type 1: Main Structural Collagen

  2. Loose Areolar Connective Tissue

  3. Dense Connective Tissue (Dense Irregular, Dense Regular)

  4. Type 2: Hyaline Cartilage Matrix

  5. Type 3: Reticular/-in Fiber

  6. Type 4: Basement Membrane

  7. Type 7: Anchoring Fibrils
• Collagenous Tissue


  Most of the components belong to the group of collagenous tissue
• Collagen is the main protein/fiber present in collagenous tissue
• Collagen


  Name for both the fiber and its protein; known for its tensile strength and protection
• Collagen decreases with age and is one of the culprits for knee problems in older people
• There are around 28 types of collagens, but the module only tackles 5 of them
• Collagen appears blue/blue green/teal in Masson trichrome stain and stains eosinophilic (pink/red) in H&E stain
• Collagen is made up of collagen fibrils, and overlapping of collagen fibrils produces its striated appearance
• Collagen fibers and fibrils consist of Collagen Bundle >> Collagen Fiber >> Collagen Fibril >> Tropocollagen
• E/M micrograph shows Type 1 collagen with visible striations due to the cross-banding of tropocollagen
• Collagen types


  • Type I
  • Type II
  • Type III
  • Type IV
• Collagen


  Source of collagen
• Tropo


  Origin
• Collagen formation


  Collagen Bundle >> Collagen Fiber >> Collagen Fibril >> Tropocollagen
• If black and white, E/M. The lack of nuclei and the visible striations (only seen in E/M) are due to the cross-banding of tropocollagen. It looks very similar to skeletal muscle, albeit the lack of peripheral nuclei.
• Type I Collagen


  • Mainly involved in the structure of connective tissues
  • Most common
  • Can be loose or dense depending on the number of fibers present
• Type I Collagen


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


  • Loose and widely distributed
  • Supports organs from strain
  • Contains few collagen fibers and other types of fibers like elastin
  • Abundant cell: Fibroblast nuclei
• Dense Connective Tissue


  • Collagen fibers are plenty and closely packed
  • Can be Dense Irregular Connective Tissue or Dense Regular Connective Tissue
• Dense Irregular Connective Tissue

  • Collagen fibers are randomly arranged
  • Found in Dermis, Capsule of organs, Perichondrium/Periosteum
• Dense Regular Connective Tissue

  • Collagen fibers are organized, oriented in one direction, and parallel to each other
  • Found in tendons, ligaments, aponeuroses
• Type II Collagen


  • Located in the Hyaline Cartilage
  • Matrix primarily made up of Type 2 collagen and chondroitin sulfate
  • Provides strength with limited mobility and flexibility
  • Most prevalent/common type of cartilage
• Type III Collagen


  • Composed of type III collagen secreted by reticular cells
  • Forms the supporting framework of hematopoietic organs like the liver and spleen
  • Stains black with silver salts - argyrophilic
• Type IV Collagen


  • Forms the Basement Membrane