Epithelial tissue forms protective, closely packed sheets that cover body surfaces, line internal spaces, and make up glands. Understanding its basic features and classification helps explain how different epithelial tissues are suited to protection, absorption, filtration, and secretion.
Epithelium, also called epithelial tissue, is a thin, continuous layer of cells with very little extracellular matrix between them. Its cells are tightly packed, forming a sheet that covers the outer body surface or lines organs, body cavities, and vessels. The epidermis, the outermost layer of skin, is one example.
All flashcards
What is epithelial cell polarity?
Epithelial cells have distinct surfaces: the basal surface rests on the basement membrane, while the apical surface faces a cavity, lumen, or external environment.
What are the two layers of the basement membrane, and what do they contain?
The basal lamina contains laminin secreted by epithelial cells; the reticular lamina contains collagen secreted by connective tissue.
How does pseudostratified epithelium differ from truly stratified epithelium?
Pseudostratified epithelium is one layer, with every cell contacting the basement membrane; stratified epithelium has multiple layers.
How do endocrine and exocrine glands differ in how they release products?
Endocrine glands release products into surrounding extracellular space for uptake by the circulation; exocrine glands deliver products through ducts.
What is the usual name for cancer arising in true epithelial tissue?
Carcinoma.
Quiz questions
How does an endocrine gland release its products?Answer: Into surrounding extracellular space, from which they enter the circulation.
What is the main role of epithelial tight junctions?Answer: They seal spaces between adjacent cells and limit paracellular leakage.
Which structures are lined by endothelium?Answer: Blood vessels, lymphatic vessels, and the heart.
What is a function of primary cilia on epithelial cells?Answer: Sensing chemical, temperature, and mechanical cues in the environment.
Which intermediate filament protein can help identify epithelial cells?Answer: Cytokeratin.
Based on the Wikipedia article Epithelium, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.