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Chapter 4: Histology

Introduction to Tissue

  • Definition of Tissue: Composed of cells and extracellular matrix.

  • Components of Tissue:

    • Cells

    • Extracellular Matrix (ECM)

Extracellular Matrix and Tissue Types

  • Tissue Decision Tree for Non-Excitable Tissues:

    • Tightly-packed cells with little to no matrix = Epithelium

    • Fewer cells with larger quantities of matrix = Connective Tissue

  • Main Cell Types in Connective Tissue:

    • Fibroblast

    • Other specific cell types

Classification of Connective Tissue

  • Connective Tissue Proper (CTP):

    • Divided into Loose and Dense CTP

    • Loose (Areolar) CTP: More ground substance (GS), fewer fibers

    • Dense CTP: Packed fibers, less ground substance

Microscopic Observations of Tissues

  • Colored Scanning Electron Microscopy (SEM):

    • Displays fat cells (adipocytes) surrounded by fine protein fibers.

    • Identifying cell types through staining:

      • Dark circles = nuclei (indicate epithelium presence)

      • Bright red cells without nuclei = red blood cells (indicative of blood vessels)

      • Connective tissue often has numerous blood vessels.

Types of Epithelial Tissues

  • Structural Classification:

    • Simple Epithelium: Single layer (includes columnar, cuboidal, squamous)

      • Examples:

        • Simple Squamous Epithelium

        • Simple Cuboidal Epithelium

        • Simple Columnar Epithelium

        • Pseudostratified Columnar Epithelium (also simple)

    • Stratified Epithelium: Multiple layers (includes stratified squamous, transitional)

      • Examples:

        • Stratified Squamous Epithelium

        • Transitional Epithelium (also stratified)

Cellular Junctions and Functions

  • Importance of cellular junctions in epithelial tissues.

Disease Consideration

  • Epithelial Cell Cancer: Commonly referred to as carcinoma.

Cells of Connective Tissue Proper

  • Types of Connective Tissue Proper:

    • Loose (Areolar) Connective Tissue

    • Dense Irregular Connective Tissue

    • Dense Regular Collagenous Connective Tissue

    • Reticular (Connective) Tissue

    • Adipose (Connective) Tissue