Overview
This lecture explains how epithelial tissues are named based on cell layers and cell shapes, and introduces special types of epithelium found in the human body.
Naming of Epithelial Tissue
- Epithelial tissue names have two parts: the first indicates cell layers, the second indicates cell shape.
- "Simple" epithelium has one layer of cells; allows rapid absorption or diffusion.
- "Stratified" epithelium has multiple layers; provides protection against abrasion, friction, or bacteria.
Cell Shape Types
- "Squamous" epithelium cells are flat.
- "Cuboidal" epithelium cells are cube-shaped.
- "Columnar" epithelium cells are column-shaped.
Common Epithelial Types & Their Locations
- Simple squamous: one flat cell layer; allows rapid passage of materials.
- Simple cuboidal: one cube-shaped cell layer; found in areas needing absorption or secretion.
- Simple columnar: one column-shaped cell layer; specialized for absorption and secretion.
- Stratified squamous: multiple flat cell layers; found in skin and areas needing protection.
- Stratified cuboidal and stratified columnar: rare, found in certain glands.
Special Epithelial Types
- Pseudostratified columnar: appears layered but all cells touch basement membrane; secretes mucus and has cilia; found in nasal cavity and trachea.
- Transitional epithelium: a stratified type that stretches; found in the bladder; cells change from cuboidal (empty bladder) to squamous (full bladder).
Key Terms & Definitions
- Simple epithelium — one cell layer thick.
- Stratified epithelium — multiple cell layers thick.
- Squamous — flat-shaped epithelial cells.
- Cuboidal — cube-shaped epithelial cells.
- Columnar — column-shaped epithelial cells.
- Pseudostratified — falsely appears stratified; all cells touch basement membrane.
- Transitional epithelium — stratified tissue that stretches and changes shape.
Action Items / Next Steps
- Review examples of each epithelial type and their locations.
- Memorize the naming convention for epithelial tissues.