Lecture Notes: Connective Tissue

Overview of Connective Tissue

• Connective tissues consist of cells surrounded by an extracellular matrix.
• Extracellular Matrix:
  • Composed of ground substance (a fluidy substance) and fibers made of proteins.
• Functions:
  • Structural support (skeletal system).
  • Transportation of substances within the body.
  • Protection of organs.
  • Energy storage.
  • Immune response and pathogen defense.
  • Sensory functions.
• Most connective tissues are vascularized (except cartilage).

Components of the Extracellular Matrix

• Ground Substance: Colorless, viscous fluid surrounding cells.
• Fibers: Vary the characteristics/properties of connective tissue.
  • Collagen Fibers: Strong, provide strength and resistance to tissues (e.g., tendons, ligaments).
  • Reticular Fibers: Form a network (stroma); found in organs like liver and spleen.
  • Elastic Fibers: Made of elastin; allow tissues to stretch and recoil.

Types of Connective Tissue

• Connective Tissue Proper:
  • Classified into loose or dense based on structure.
  • Loose Connective Tissue:
    • Areolar Tissue: Least specialized, loose organization.
    • Adipose Tissue: Fat storage, insulation.
    • Reticular Tissue: Network support structure (not studied in lab).
  • Dense Connective Tissue:
    • Dense Regular: Parallel collagen fibers (e.g., tendons).
    • Dense Irregular: Densely packed but random organization (e.g., skin).
    • Elastic Tissue: Contains elastic fibers, provides elasticity.
• Fluid Connective Tissue:
  • Blood: Cells and plasma; includes erythrocytes, leukocytes, and platelets.
  • Lymph: Part of the lymphatic system, immune functions.
• Supporting Connective Tissue:
  • Cartilage: Gel matrix, shock absorption (e.g., end of long bones).
    • Types: Hyaline, Elastic, Fibrocartilage.
  • Bone (Osseous Tissue): Calcified, rigid matrix.
    • Osteocytes: Cells housed in lacunae.
    • Canaliculi: Channels for communication between osteocytes.

Functions of Cells in Connective Tissue

• Fibroblasts: Secrete proteins for fiber formation.
• Fibrocytes: Maintain connective tissue.
• Adipocytes: Store fat.
• Mesenchymal Cells: Stem cells for regeneration.
• Macrophages: Phagocytic, clean debris/pathogens.
• Mast Cells: Involved in inflammation.
• Lymphocytes: Immune function, antibody production.
• Microphages: Smaller phagocytic cells.
• Melanocytes: Contain melanin, provide coloration.

Detailed Examination of Tissues

• Areolar Connective Tissue: Loose structure, diverse cell types.
• Adipose Tissue: Fat storage, nuclei pushed to cell periphery.
• Dense Regular Connective Tissue: Parallel collagen fibers, organized.
• Dense Irregular Connective Tissue: Random fiber organization, resilient.
• Cartilage Types:
  • Hyaline: Common, found in joints.
  • Elastic: Flexible, found in ears.
  • Fibrocartilage: Strong, found in vertebrae.

Notes on Bone Structure

• Osteons: Functional unit, looks like tree rings.
• Central Canal: Contains blood supply.
• Lamellae: Concentric rings in osteons.
• Periosteum: Membranous layer surrounding bone.