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Epithelial tissue

Epithelial tissue. Functions Absorption Excretion Filtration Secretion Protection Sensory reception. Characteristics of epithelium. Cellularity Tightly packed cells Forms sheet Little extracellular materials Specialized contacts Tight junction Desmosomes.

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Epithelial tissue

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  1. Epithelial tissue • Functions • Absorption • Excretion • Filtration • Secretion • Protection • Sensory reception

  2. Characteristics of epithelium • Cellularity • Tightly packed cells • Forms sheet • Little extracellular materials • Specialized contacts • Tight junction • Desmosomes

  3. Characteristics of epithelium • Polarity • Apical surface • Upper surface exposed to the outer environment • Specialized structures • Microvilli • Basal surface • Lined with basal lamina • Thin membrane Apical Surface Basal Surface Basal Lamina

  4. Characteristics of epithelium • Supported by connective tissue • Basement membrane • Basal lamina • Composed of glycoproteins • Reticular lamina • Composed of collagens • Tougher than basal lamina • Resists stretching • Define epithelial boundary

  5. Characteristics of epithelium • Innervated • Nerve endings • Avascular • Utilizes nutrients diffused from blood vessels underlining connective tissue • Highly regenerative • Many epithelial cells are exposed to extreme external environment

  6. Classification of epithelia • Based on the number of cell layers • Simple • Stratified • Simple epithelia • Absorption/filteration • Stratified epithelia • Extreme environment

  7. Classification of epithelia • Based on the shape of cells • Squamous • Flat, scale-like cells • Cuboidal • Box-like cells • Height/width = 1 • Columnar • Tall, column-like cells • Shape of the nucleus • Reflects cell shape

  8. Simple epithelia • Simple squamous epithelium • Flat cells • Looks like tiled floor • Found in tissues involved in rapid exchange of materials • Lungs • Kidneys

  9. Simple epithelia • Special simple squamous epithelia • Endothelium • Inner lining of blood vessels and lymphatic vessels • Extremely thin • Mesothelium • Membrane that covers chest and abdominal cavity and organs found in these cavities

  10. Simple epithelia • Simple cuboidal epithelium • cube-like cells • Found in tissues involved in secretion and absorption • Kidneys

  11. Simple epithelia • Simple columnar epithelium • Tall, column-like cells • Found in digestive tract • Absorption • Secretion • Goblet cells produce protective mucus • Ciliated

  12. Psuedostratified columnar epithelium • Cells vary in their height • Tallest cells interact with external environment • Shorter cells serve as reserves • False appearance of stratification • Location of nuclei within the layer

  13. Psuedostratified columnar epithelium • Involved in secretion and absorption • Ciliated • Removal of particles within the air

  14. Stratified epithelia • Multiple layers of cells • cells in lower layers • Replacement • More durable • Protective covering

  15. Stratified epithelia • Stratified squamous epithelia • Most wide spread • Cells on the apical surface • Squamous • Basal cells • Cuboidal or columnar • Different cell viability

  16. Stratified epithelia • Stratified squamous epithelia • The outer layer (epidermis) • Keratinized in skin because of protective protein called keratin

  17. Stratified epithelia • Stratified cuboidal epithelium • Very rare • Found in large glands (sweat, mammary) • Usually contains two layers of cells • Stratified columnar epithelium • Very rare • Only its top layer contains columnar cells

  18. Transition epithelium • Found in organs that stretches • Urinary bladder • Basal cells • Columnar or cuboidal • Apical cells • Vary in appearance depends on how much distention the organ undergoes

  19. Transition epithelium • Changes the number of cell layers as the organ distends • 6 to 3 when the bladder stretches with urine • Apical cells flatten and look like squamous cells

  20. Glandular epithelia • Glands • Composed of cells involved in production and secretion of product • Fluid-like • Proteins • Lipids • Secretion • Active process

  21. Glandular epithelia • Glands • Location of secretion • Endocrine (within the body) • Exocrine (outside of the body) • Number of the cells that compose the gland • Unicellular • Multicellular • Ducts

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