Overview
This lecture covers techniques to identify different types of epithelial tissue based on cell layer number and cell shape, with practical slide examples and naming conventions.
Identifying Epithelium: Key Questions
- Ask: How many layers of cells are present?
- Ask: What is the shape of the visible cells?
Types of Epithelium by Layers
- One layer of cells is called "simple" epithelium.
- Multiple layers of cells are called "stratified" epithelium.
- Pseudostratified looks layered but all cells touch the basement membrane.
Types of Epithelium by Cell Shape
- Squamous: flat cells ("squashed pancakes").
- Cuboidal: cube-shaped cells with round nuclei.
- Columnar: column-shaped cells with oval nuclei.
Special Identification Tips
- Cuboidal vs. columnar: Check nuclei shape—round for cuboidal, oval for columnar.
- Basement membrane: All epithelial tissue is attached to it.
- Goblet cells (mucus-producing): Commonly found in simple columnar epithelium.
- Cilia: Presence indicates ciliated pseudostratified columnar epithelium.
- Pseudostratified epithelium has nuclei at different heights but is one layer.
Common Examples & Naming
- Simple cuboidal: Single layer, square cells, round nuclei.
- Simple columnar: Single layer, tall cells, oval nuclei, sometimes goblet cells.
- Simple squamous: Single layer, flat cells, often seen in lung slides.
- Stratified squamous: Multiple layers, flat cells at the top.
- Transitional: Stratified, cells on top look bubbly, not clearly squamous, cuboidal, or columnar.
- Ciliated pseudostratified columnar: One layer, varying cell heights, cilia, all cells touch basement membrane.
Key Terms & Definitions
- Epithelium — tissue composed of one or more layers of cells covering surfaces or lining cavities.
- Basement membrane — thin layer anchoring epithelium to underlying tissue.
- Goblet cell — specialized cell that secretes mucus.
- Cilia — hair-like structures on cell surface for movement.
- Transitional epithelium — stratified epithelium with flexible, bubble-shaped surface cells, found in urinary tract.
- Pseudostratified — appears layered but all cells touch the basement membrane.
Action Items / Next Steps
- Practice identifying epithelial tissues under the microscope using layer count and cell shape.
- Review definitions of key epithelium types.
- Prepare for questions distinguishing closely related epithelial types.