Overview
This lecture focused on identifying different types of epithelial tissue based on the number of cell layers and cell shapes, including techniques and key characteristics used in histology.
Identifying Epithelium
- First, determine the number of cell layers: one layer is "simple," more than one is "stratified."
- Assess cell shape: squamous (flat), cuboidal (square), columnar (tall/rectangular).
- Check nuclei shape: circular nuclei suggest cuboidal, oval nuclei indicate columnar cells.
- Always identify the basement membrane, as all epithelium is attached to it.
Types of Epithelia & Key Features
- Simple Cuboidal: One layer of square cells with circular nuclei.
- Simple Columnar: Single layer of tall cells with oval nuclei, sometimes containing goblet cells.
- Simple Squamous: Single layer of flat cells, nuclei appear flattened.
- Ciliated Pseudostratified Columnar: Appears multi-layered but all cells touch the basement membrane; has cilia and columnar cells.
- Stratified Squamous: Multiple layers; topmost cells are flat, lower cells may be cuboidal but only the surface layer defines the type.
- Transitional Epithelium: Multiple layers, cells at the top look dome-shaped or like bubbles; doesn’t fit squamous, cuboidal, or columnar shapes.
Identification Examples & Hints
- Goblet cells often indicate simple columnar epithelium.
- Cilia on the surface indicate ciliated pseudostratified columnar epithelium.
- Transitional epithelium is stratified and has a bubble-like surface.
- In some tissues (like kidney), simple cuboidal cells’ nuclei may appear in a circular "cheerio" pattern.
Key Terms & Definitions
- Epithelium — Tissue type that lines surfaces and cavities, always attached to a basement membrane.
- Simple Epithelium — Single layer of cells.
- Stratified Epithelium — Multiple layers of cells.
- Squamous — Flat, pancake-shaped cells.
- Cuboidal — Cube or square-shaped cells.
- Columnar — Tall, rectangular cells.
- Pseudostratified — Appears layered but all cells touch the basement membrane.
- Goblet cell — Specialized cell that secretes mucus, often found in simple columnar epithelium.
- Basement membrane — Thin layer anchoring epithelium to underlying tissue.
Action Items / Next Steps
- Practice identifying epithelial types in histology slides using layer number and cell shape.
- Review slides for the presence of goblet cells, cilia, and the basement membrane.