Lecture Notes on Epithelial Tissue

Introduction

• Role of Epithelial Tissue: Separates and organizes complex systems in the body.
• Analogy: Compared to organizing a messy lunchroom to maintain order.

Types of Epithelial Tissue

1. Proper Epithelium

   • Lines outer and inner body.
   • Covers body surfaces, lines cavities, and coats organs.

2. Glandular Epithelium

   • Forms glands and secretes hormones and other substances.

Functions of Epithelial Tissue

• Protection: Prevents injury and infection.
• Partitioning: Organizes body into separate units.
• Secretion: Involved in secretion of mucus, hormones, etc.

Characteristics of Epithelial Tissue

• Avascular: No direct blood supply; depends on surrounding tissues.
• Polar: Has distinct apical (outer) and basal (inner) sides.
• Selective Permeability: Allows absorption, filtration, and excretion.

Classification by Shape and Layering

Shapes

• Squamous: Flat, scale-like, easy for material transfer.
• Cuboidal: Cube-shaped, involved in absorption and secretion.
• Columnar: Tall, column-like, cushions underlying tissues.

Layering

• Simple Epithelium: Single layer of cells.
• Stratified Epithelium: Multiple layers for protection.
• Pseudostratified Epithelium: Appears layered but isn't.

Functions Related to Structure

• Squamous Cells: Found in areas where absorption or transport is key, e.g., air sacs in lungs.
• Cuboidal/Columnar Cells: Found where secretion is needed, e.g., stomach lining.
• Stratified Squamous: Found in areas with high wear and tear, e.g., skin, mouth.

Glandular Epithelium

• Endocrine Glands: Secrete hormones into bloodstream, e.g., thyroid gland.
• Exocrine Glands: Secrete substances through ducts, e.g., sweat, saliva.

Importance

• Key role in bodily interactions with the environment.
• Ensures proper functioning by maintaining boundaries and enabling secretion.

Conclusion

• Epithelial Tissue: Essential for creating inner and outer boundaries, maintaining order, and enabling secretion.

Acknowledgments

• Written by Kathleen Yale.
• Edited by Blake deBestino.
• Consultant: Dr. Brandon Jackson.
• Directed and edited by Nicholas Jenkins.
• Script supervisor: Sarah Miesmer.
• Sound design by Michael Aranda.
• Graphics by Thought Cafe.