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Chapter 4: Histology

Introduction to Tissue

  • Tissue: Consists of cells and extracellular matrix (ECM).

  • Main components of tissue include cells and their surrounding matrix.

Types of Tissues

  • Excitable Tissues: Not covered in detail here.

  • Non-Excitable Tissues: Classifications based on cell density and matrix composition.

Tissue Decision Tree for Non-Excitable Tissues

  • Tightly-packed cells with little to no matrix:

    • Indicates Epithelium.

  • Fewer cells with a larger quantity of matrix:

    • Indicates Connective Tissue.

Types of Connective Tissue

  • Fibroblast: Main cell type in connective tissue.

  • Connective Tissue Proper vs Specialized Connective Tissue:

    • Connective Tissue Proper (CTP):

      • Contains fibroblasts as the primary cell type.

    • Specialized Connective Tissue:

      • Different characteristics and functions.

Matrix Composition

  • Loose (Areolar) CTP:

    • More ground substance (GS), fewer fibers.

  • Dense CTP:

    • Packed fibers, less ground substance.

Observational Note

  • Tissue appearance:

    • Common observation: "But it all looks pink!"

    • Dark circles represent nuclei, indicating the presence of epithelium underneath which is connected to connective tissue.

    • Bright red cells without nuclei are identified as red blood cells indicating blood vessels in connective tissue.

Epithelial Tissue Classification

  • Simple Epithelia: One layer of cells.

    • Includes:

      • Simple squamous epithelium

      • Simple cuboidal epithelium

      • Simple columnar epithelium

      • Pseudostratified columnar epithelium (is technically simple)

  • Stratified Epithelia: Multiple cell layers.

    • Includes:

      • Stratified squamous epithelium

      • Transitional epithelium (also stratified)

Epithelial Cell Functionality

  • Transport Across Simple Epithelia:

    • Highlights the specific function and utility of simple epithelial types.

Epithelial Cell Cancer

  • Carcinoma: Refers to cancer developed in epithelial cells.

Summary of Connective Tissue Types

  • Cells of Connective Tissue Proper include:

    • Loose (Areolar) Connective Tissue

    • Dense Irregular Connective Tissue

    • Dense Regular Collagenous Connective Tissue

    • Reticular Tissue

    • Adipose Tissue