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Understanding Epithelial Tissues: Classifications and Functions

Epithelial tissue, a major tissue type lacking blood supply, lines body surfaces and glands. Explore the types and layers of epithelium, such as squamous, cuboidal, columnar, and transitional, and their roles in protection and absorption.

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Understanding Epithelial Tissues: Classifications and Functions

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  1. Tissues Groups of cells performing specialized roles

  2. 4 Major Tissue Types • Epithelial tissue • Connective tissue • Muscle tissue • Nervous tissue

  3. Epithelial tissue Widespread throughout the body Lines all body surfaces inside and out Major tissue of glands Lacks blood supply (avascular) Reproduces quickly Tightly packed—good barriers Control permeability

  4. Classification of Epithelium Tissue 1. Shape of the cells Squamous • Cells are thin and flat  • Often display many angular outlines when viewed from above  Cuboidal • Cells are approximately as tall as wide  Columnar • Cells are definitely more taller than wide 

  5. Simple  • Only one layer of cells  • All cells touch the basement membrane  Stratified • There is more than one layer of cells  • Only the lowest cells rest on the basement membrane  • Other cells are stacked upon each other in various configuration making up the "layers"  2. The number of cell layers present

  6. Simple Squamous Epithelium • Single layer of thin flattened cells • Functions in diffusion • Lines air sacs of lungs and blood vessels

  7. Simple Cuboidal Epithelium • Single layer of cube shaped cells • Covers ovaries, lines ducts of glands, kidney tubules • Functions in secretion & absorption

  8. Simple Columnar Epithelium • Single layer of elongated cells • Functions in protection, absorption & secretion • May have microvilli which increase surface area for absorption • May have goblet cells scattered among the columnar cells to secrete mucus • Lines stomach & intestines

  9. Pseudostratified Columnar Epithelium • Appears stratified (layered) but is not • Cells may possess cilia (hair-like projections) • May have goblet scattered throughout • Lines respiratory tract • Helps to move mucus

  10. Stratified Squamous Epithelium • Many layers of cells thick • Cells reproduce in deep layers and push older ones out • Forms outer layer of skin (epidermis) • Lines mouth, throat, vagina • Functions in protection

  11. Transitional epithelium • Specialized to undergo changes in response to increased tension • Expands and contracts • Forms lining of urinary bladder & ureters • stratified

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