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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