Epithelial tissue creates order in the body by organizing feisty and complex systems, much like separating middle-schoolers at lunch to maintain order.
It covers and lines the body, creating boundaries necessary for function.
Types of Epithelial Tissue
Proper Epithelium: Covers and lines outer and inner body surfaces.
Glandular Epithelium: Forms glands and secretes hormones and substances.
Functions of Epithelial Tissue
Protects and organizes the body, partitioning it into separate but connected units.
Covers body surfaces, lines cavities, and coats organ walls.
Acts as a barrier, protecting deeper tissues from injury or infection.
Lacks blood supply (avascular), relies on connective tissues for nutrients.
Classification by Shape & Layering
Shapes:
Squamous: Flat, scale-like, allow easy material passage.
Cuboidal: Cube-shaped, absorb nutrients, produce secretions.
Columnar: Tall, cushion tissues, manage space for secretions.
Layering:
Simple Epithelium: Single layer of cells.
Stratified Epithelium: Multiple layers, like bricks.
Pseudostratified Epithelium: Appears multilayered, but isnât.
Naming is based on layering and shape, e.g., Simple Squamous, Stratified Cuboidal.
Special Characteristics
Polar Nature: Cells have distinct sides - apical (exposed) and basal (attached to connective tissue).
Selectively Permeable: Allows absorption, filtration, and excretion.
Glandular Epithelium
Forms endocrine and exocrine glands.
Endocrine Glands: Secrete hormones directly into blood.
Exocrine Glands: Secrete substances into ducts leading outside or into body cavities.
Importance
Facilitates every interaction with the physical universe.
Vital for protection, secretion, and maintaining boundaries.
Conclusion
Epithelial tissue, though uncelebrated, plays a crucial role in maintaining body organization and function.
It is essential for both protection and secretion, ensuring the body operates efficiently.
Credits
Written by Kathleen Yale, edited by Blake de Pastino, with Dr. Brandon Jackson as consultant.