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5 epithelium sp

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    5 epithelium sp 5 epithelium sp Presentation Transcript

    • EPITHELIUM DR. SWATI PATIL
    • INTRODUCTIONEpi= upon; Thelia= nippleDEVELOPMENT Ectoderm- skin, mouth, nose and anal canal. Endoderm- GIT, glands, resp tract Mesoderm-body cavities (Mesothelium), endothelium.
    • Function of Epithelial Tissue• Protection• Absorption• Filtration• Secretion
    • Characteristics of Epithelial Tissue• Form continuous sheets (fit like tiles)
    • • Apical Surface – All epithelial cells have a top surface that borders an open space (lumen)
    • • Basement Membrane – anchors epithelial cells to underlying connective tissue
    • BASEMENT MEMBRANE- visible under LM- PAS +- comprises of basal lamina& reticular lamina
    •  BASAL LAMINA - visible in EM - 20-100 nm thick - consists of dense and clear layers - composed of macromolecules 1. Laminin 2. Type IV collagen 3. Entactin (Nidogen) 4. Proteoglycans
    • • Avascularity – Lacks blood vessels – Nourished by connective tissue• Regenerate & repair quickly
    • Classification of Epithelial Tissue
    • Classification of Epithelial Tissue - Criteria • Cell Shape – Squamous – flattened – Cuboidal - cubes – Columnar - columns
    • • Cell Layers – Simple (one layer) – Stratified (many layers) • Named after type of cell at apical surface
    • Simple Squamous Epithelium• Structure – Single Layer of flattened cells• Function – Absorption, and filtration – Not effective protection – single layer of cells.• Location – Walls of capillaries, air sacs in lungs – Form serous membranes in body cavity
    • Simple Cuboidal Epithelium• Structure – Single layer of cube shaped cells• Function – Secretion and transportation in glands, filtration in kidneys• Location – Glands and ducts (pancreas & salivary), kidney tubules, covers ovaries
    • Simple Columnar Epithelium• Structure – Elongated layer of cells with nuclei at same level• Function – Absorption, Protection & Secretion – When open to body cavities – called mucous membranes
    • Simple Columnar Epithelium• Special Features – Microvilli, bumpy extension of apical surface, increase surface area and absorption rate. – Goblet cells, single cell glands, produce protective mucus.• Location – Linings of entire digestive tract
    • Features of Apical Surface of Epithelium
    • Microvilli Finger-like extensions of plasma membrane of apical epithelial cell Increase surface area for absorption Temporary or permanent 1 µm : height, 0.8 µm : width BRUSH/STRIATED BORDER: seen in LM Terminal web : supports microvilli composed of actin filaments w/ fimbrin & villin (eg.) in small intestine
    • Features of Apical Surface of Epithelium Cilia: (eg.) respiratory tubes  Whip-like, motile extensions  Moves mucus, etc. over epithelial surface 1-way  5-10 µm : length  0.2 µm : diameter * Flagella: (eg.) spermatozoa  Extra long cilia  Moves cell
    •  Stereocilia (eg.) epididymis & ductus deferens  Longer but non motile, compared to microvilli  Branched
    • Pseudostratified Epithelium• Structure – Irregularly shaped cells with nuclei at different levels – appear stratified, but aren’t. – All cells reach basement membrane• Function – Absorption and Secretion – Goblet cells produce mucus – Cilia (larger than microvilli) sweep mucus• Location – Respiratory Linings & Reproductive tract
    • Myoepithelial cells
    • Stratified Squamous Epithelium• Structure Many layers (usually cubodial/columnar at bottom and squamous at top)Function – Protection – Keratin (protein) accumulates in older cells near the surface • waterproofs and toughens skin. Nonkeratinised• Location Keratinised
    • Stratified squmous keratinised
    • Stratified squamous non-keratinised
    • Stratified cuboidal epithelium
    • Stratified columnar epithelium
    • Transitional Epithelium• Structure – Many layers – Very specialized • cells at base are cuboidal or columnar, at surface will vary. – Change between stratified & simple as tissue is stretched out.• Function – Allows stretching (change size)• Location – Urinary bladder, ureters & urethra
    • GLANDS• One or more cells that make and secrete a product.• Secretion = protein in aqueous solution: hormones, acids, oils.• Endocrine glands – No duct, release secretion into blood vessels – Often hormones – Thyroid, adrenal and pituitary glands• Exocrine glands – Contain ducts, empty onto epithelial surface – Sweat, Oil glands, Salivary glands, Mammary glands.
    • Modes of Secretion• (How the gland’s product is released)• Merocrine - secretory products are released by exocytosis – Ex: Sweat glands and salivary glands• Apocrine -apical part is shed off to discharge – secretion - Ex:mammary glands
    • Modes of Secretion• Holocrine – Entire cell disintegrates while discharging its secretion – Sebaceous (oil glands on the face) only example
    • Classification of Exocrine glandsBranching  Simple – single, unbranched duct  Compound – branched.
    • • Shape: – tubular or alveolar – Tubular – shaped like a tube – Alveolar – shaped like flasks or sacs – Tubuloalveolar – has both tubes and sacs in gland
    • Cell Junctions & Cell-Cell Adhesion
    • Classification of cell contacts• Unspecialised contacts -cell adhesion molecule -intermediate protein
    • Actin cytoskeleton dependent cell-cell and cell-ECM adhesions Cell-cell adherence junctions 1. Calcium-dependent  Cadherins  Selectins  Integrins 2. Calcium-independent  Neural cell adhesion molecule  Intercellular adhesion molecule
    • • Specialized contacts -Anchoring junctions 1.Adhesive spots or desmosomes or macula adherens 2.Adhesive belts or zona adherens 3.Adhesive strips or fascia adherens - Occluding junction or zonula occludens or tight junction -Communicating junctions or gap junctions
    • Desmosomes
    • Zonula adherens
    • Fascia adherens
    • Desmosomes &hemidesmosomes
    • Focal adhesion plaques
    • Tight Junctions
    • Types of Cell Junctions
    • Summary of cell junctions
    • Thank you