Study Notes on Connective Tissue

CONNECTIVE TISSUE OVERVIEW

  • Comprises various cells within a specialized extracellular matrix (ECM).
  • Functions:
    • Supports and connects tissues and cells, forming organs.
    • Provides metabolic support via nutrient and waste diffusion.

CELL POPULATIONS IN CONNECTIVE TISSUE

  • Resident Cells:
    • Fibroblasts, Macrophages, Adipocytes, Mast cells, Adult Stem Cells
  • Transient Cells:
    • Lymphocytes, Plasma cells, Neutrophils, Eosinophils, Basophils, Monocytes

EXTRACELLULAR MATRIX (ECM)

  • Consists of protein fibers and ground substance:
    • Protein Fibers: Collagen, Elastic, Reticular
    • Ground Substances: Proteoglycans, Multiadhesive glycoproteins, Glycosaminoglycans (GAGs)
  • Functions of ECM:
    • Mechanical support, Influences communication, Pathways for cell migration.

GROUND SUBSTANCE

  • Fills spaces between cells/fibers.
  • Structure:
    • Composed of proteoglycans, GAGs, and multiadhesive glycoproteins.
    • Highly hydrated, acts as a lubricant and barrier.
  • Staining: Typically lost in routine preparations, identifiable in special stains.

GLYCOSAMINOGLYCANS (GAGS)

  • Physical properties dependent on GAGs; GAGs are long polymers.
  • Major types include Hyaluronan, Chondroitin sulfate, Dermatan sulfate, Keratan sulfate, Heparan sulfate.
  • Charged nature attracts water, forms hydrated gel for diffusion.

PROTEOGLYCANS

  • Composed of GAGs attached to core proteins.
  • Functions in ECM hydration, collagen organization, and cell interactions.

DISORDERS RELATED TO COLLAGEN SYNTHESIS

  • Hurler Syndrome: Enzyme deficiency, accumulation of dermatan/heparan sulfate, leads to various systemic issues.
  • Hunter Syndrome: Lack of iduronate-2-sulfatase, causes organ dysfunction.
  • Marfan Syndrome: Caused by fibrillin mutation, affects elastic fibers leading to aortic risk.

CONNECTIVE TISSUE CLASSIFICATION

  • **Types: **
    • Connective Tissue Proper (Loose/Dense)
    • Embryonic Connective Tissue (Mesenchyme, Mucous)
    • Specialized Connective Tissues (Cartilage, Bone, Blood)
  • Dense Connective Tissue:
    • Regular and irregular types.

FIBER TYPES IN CONNECTIVE TISSUE

  • Collagen Fibers: Most abundant, provide tensile strength, appear banded with TEM.
  • Reticular Fibers: Type III collagen, form supportive frameworks.
  • Elastic Fibers: Composed of elastin, allow tissue stretch.

FIBROBLASTS

  • Principal cell type in connective tissue; synthesize ECM components and fibers.
  • Myofibroblasts: Active in wound contraction.

MACROPHAGES

  • Phagocytic cells, important for defense and cleanup.
  • Present throughout connective tissues, derived from monocytes.

MAST CELLS

  • Release mediators involved in inflammation and allergic responses.
  • Two types identified based on location and secreted substances.

ADIPOCYTES

  • Store fat, involved in hormone and mediator synthesis.

STEM CELLS

  • Adult stem cells found in niches, contribute to tissue repair and maintenance.

LYMPHOCYTES AND PLASMA CELLS

  • Lymphocytes: Key players in immune responses.
  • Plasma Cells: Produce antibodies, found in areas prone to antigen exposure.

CLINICAL CONDITIONS

  • Ehlers-Danlos Syndromes: Affect connective tissues leading to various physical manifestations.
  • Scurvy: Vitamin C deficiency affecting collagen synthesis.