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Structure of Skin by Aseem

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A basic Dermatology presentation (PPT) showcasing the structure and functions of Skin, the largest organ of the human body!

Structure of Skin by Aseem

  1. 1. STRUCTURE OF SKIN Dr Aseem Sharma Dermatology Resident
  2. 2. INTRODUCTION • Surface Area 1.62/ 1.45 sq metres (M/F) • 16 – 20% Body Weight (approx 5 kg) • Largest Organ
  3. 3. TYPES OF SKIN • 02 Types : GLABROUS (Non-Hairy) ‘Dermatolglyphics’ NON-GLABROUS (Hair-bearing)
  4. 4. LAYERS OF THE SKIN EPIDERMIS CUTICLE/EPITHELIUM DERMIS HYPODERMIS/PANNICULUS ADIPOSUS - SUBCUTIS
  5. 5. APPENDAGES OF THE SKIN • Hair • Nails • Glands 1. Eccrine 2. Apocrine 3. Sebaceous
  6. 6. EMBRYOLOGY SPECIFICATION : Commitment 0-2 months FL MORPHOGENESIS: Specialization 2-5 months FL DIFFERENTIATION: Maturation 5-9 months FL
  7. 7. EMBRYOLOGICAL ORIGINS ECTODERMAL : Epidermis, Pilosebaceous Unit, Eccrine Gland, Nail NEURO-ECTODERMAL : Melanocytes, Nerves, Sensory Receptors MESODERMAL : Dermis, Hypodermis, Muscle, Adipocytes, Blood Vessels, Mast Cells, Langerhan’s cells, Macrophages
  8. 8. EMBRYOLOGY • EPIDERMIS (ECTODERMAL) 3rd Week FL - Single layer 6th Week FL - Periderm + Germinative Layer 10th Week FL - Hemi-Desmosomal/Desmosomal Protein 11th Week FL - Intermediate Layer 12-16th Week - Microvilli 20th Week - KERATOHYALINE granules in Intermedicate Layer, Germinative Layer proliferation, Epidermal Cornification 24th Week - Vernix Caseosa shed; Keratinization done
  9. 9. EMBRYOLOGY • DERMIS (MESENCHYME) 4TH Week FL - Collagen Fibres 6th Week FL - Touch Pads (Extremities) 8 – 14th Week FL - Melanoblasts, Phagocytes 14 – 22nd Week FL - Fibroblasts, Merkel, Mast Cells 22nd Week FL – Elastin Fibres
  10. 10. EMBRYOLOGY • HYPODERMIS (MESENCHYME) 14 Weeks FL - Lipoblasts  Lipocytes
  11. 11. EPIDERMIS • Stratified Squamous Epithelium • Variable Thickness 0.4 – 1.5 mm • Cellular Components : 95% Keratinocytes 5% Merkel, Melanocytes, Langerhans
  12. 12. 8/5/2013 14 STRATUM BASALE • Stratum Germinativum • Small, Continuous, Cuboidal, 1-cell thick, Nucleated • Dense cytoplasm, Dark staining Nuclei; Cell division q 18-19 days • Transient amplifying cells Post-Mitotic cells Epidermal stem cells
  13. 13. STRATUM SPINOSUM • Prickle-Cell layer • Desmosomes  Spines • 8-10 cell layers, Nucleated • Large, Flattened, Polyhedral cells
  14. 14. 8/5/2013 16 STRATUM GRANULOSUM • Intracellular Basophilic Keratohyaline granules • 2-5 cell layer, Nucleated • Odland Bodies/ Lamellar Granules – facilitate desquamation
  15. 15. 8/5/2013 17 STRATUM LUCIDUM • Glabrous Skin only • ‘Electron-Luscent’ • Nucleated, Transitional Cells
  16. 16. STRATUM CORNEUM • Outermost Skin Layer • 20-25 Cell layer • Corneocytes - Enucleated, minus Cytoplasmic Organelles, Terminally Differentiated; ‘Soft Keratin’
  17. 17. DERMIS • 10-40 X thicker than Epidermis • Variable thickness 1-5 mm • Fibrous, Filamentous, Amorphous Connective Tissue with Nerves, Vessels and embedded in Ground Substance • Restructuring/ Remodelling • Pliablility, Elasticity, Tensile Strength
  18. 18. PAPILLARY DERMIS • 1/10th of Dermis; Interdigitates with Epidermal Rete Ridges. • Small Diameter COLLAGEN Fibres • OXYTALAN ELASTIC Fibres • Higher Metabolic Rate; Loose Connective tissue
  19. 19. RETICULAR DERMIS • 9/10th of Dermis; Merges with Underlying Subcutaneous Fat • Large Diameter COLLAGEN Fibres • ELAUNIN ELASTIC Fibres • Densely-packed Connective Tissue
  20. 20. COMPONENTS OF DERMIS ACELLULAR (MAJOR COMP) GROUND MATRIX CONNECTIVE TISSUE MATRIX (Collagen/Elastin) CELLULAR FIBROBLASTS MACROPHAGES/MONOCYTES/DENDROCYTES MAST CELLS
  21. 21. GROUND SUBSTANCE • Amorphous, supporting Matrix • Proteoglycans & Glycosaminoglycans • 0.2 % of the dry weight of Dermis; can bind up water upto 1000 times its volume • Binds Growth Factors
  22. 22. GROUND SUBSTANCE PGs Chondroitin Sulfates Dermatan Sulfates Heparan Sulfates GAGs Hyaluronan
  23. 23. COLLAGEN • Soft, Flexible BUT Strong, Inelastic • 75% of dry weight of DERMIS Type I 80-90% Dermis Type II 8-10% Dermis Type III Papillary Dermis Type IV Basement Membrane Type V < 5% Dermis Type VI Inter-Fibrillar Spaces Type VII Anchor Fibrils in DEJ
  24. 24. ULTRASTRUCTURE COLLAGEN • Triple Helical Conformation • (Glycine-X-Y) X - Proline Y - Hydroxyproline Glycosylated  Interchain Bonding  Secreted  Cleaved  Cross-Linked
  25. 25. 8/5/2013 28 ELASTIC FIBRES • 4% of dry weight of Dermis • Impart the property to regain original shape after deforming forces are removed • Maintain normal Skin Configuration • Elastogenesis by Microfibril deposition
  26. 26. HYPODERMIS • PANNICULUS ADIPOSUS/ SUBCUTIS • Insulating layer of Adipocytes
  27. 27. THANK YOU

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