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Epithelial tissue Functions –Absorption –Excretion –Filtration –Secretion –Protection –Sensory reception.

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Presentation on theme: "Epithelial tissue Functions –Absorption –Excretion –Filtration –Secretion –Protection –Sensory reception."— Presentation transcript:

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 Basal Surface Apical 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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