Structure of Skin by Aseem
-
Upload
aseem-sharma -
Category
Education
-
view
504 -
download
0
description
Transcript of Structure of Skin by Aseem
STRUCTURE OF SKIN
Dr Aseem SharmaDermatology Resident
INTRODUCTION
• Surface Area 1.62/ 1.45 sq metres (M/F)
• 16 – 20% Body Weight (approx 5 kg)
• Largest Organ
TYPES OF SKIN
• 02 Types :
GLABROUS (Non-Hairy) ‘Dermatolglyphics’ NON-GLABROUS (Hair-bearing)
LAYERS OF THE SKIN
EPIDERMIS CUTICLE/EPITHELIUM
DERMIS
HYPODERMIS/PANNICULUS ADIPOSUS - SUBCUTIS
APPENDAGES OF THE SKIN• Hair
• Nails
• Glands1. Eccrine2. Apocrine3. Sebaceous
EMBRYOLOGY
SPECIFICATION : Commitment 0-2 months FL
MORPHOGENESIS: Specialization 2-5 months FL
DIFFERENTIATION: Maturation 5-9 months FL
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
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
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
EMBRYOLOGY
• HYPODERMIS (MESENCHYME)
14 Weeks FL - Lipoblasts Lipocytes
EPIDERMIS
• Stratified Squamous Epithelium• Variable Thickness 0.4 – 1.5 mm• Cellular Components : 95% Keratinocytes 5% Merkel, Melanocytes, Langerhans
12/04/2023 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
STRATUM SPINOSUM
• Prickle-Cell layer
• Desmosomes Spines
• 8-10 cell layers, Nucleated
• Large, Flattened, Polyhedral cells
12/04/2023 16
STRATUM GRANULOSUM
• Intracellular Basophilic Keratohyaline granules
• 2-5 cell layer, Nucleated
• Odland Bodies/ Lamellar Granules – facilitatedesquamation
12/04/2023 17
STRATUM LUCIDUM
• Glabrous Skin only
• ‘Electron-Luscent’
• Nucleated, Transitional Cells
STRATUM CORNEUM
• Outermost Skin Layer
• 20-25 Cell layer
• Corneocytes - Enucleated, minus Cytoplasmic Organelles, Terminally Differentiated; ‘Soft Keratin’
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
PAPILLARY DERMIS
• 1/10th of Dermis; Interdigitates with Epidermal Rete Ridges.
• Small Diameter COLLAGEN Fibres
• OXYTALAN ELASTIC Fibres
• Higher Metabolic Rate; Loose Connective tissue
RETICULAR DERMIS
• 9/10th of Dermis; Merges with Underlying Subcutaneous Fat
• Large Diameter COLLAGEN Fibres
• ELAUNIN ELASTIC Fibres
• Densely-packed Connective Tissue
COMPONENTS OF DERMIS
ACELLULAR (MAJOR COMP)
GROUND MATRIX CONNECTIVE TISSUE MATRIX (Collagen/Elastin)
CELLULAR
FIBROBLASTS MACROPHAGES/MONOCYTES/DENDROCYTES MAST CELLS
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
GROUND SUBSTANCE
PGs Chondroitin Sulfates Dermatan Sulfates Heparan Sulfates
GAGs Hyaluronan
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
ULTRASTRUCTURE COLLAGEN
• Triple Helical Conformation
• (Glycine-X-Y) X - Proline Y - Hydroxyproline Glycosylated Interchain Bonding Secreted
Cleaved Cross-Linked
12/04/2023 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
HYPODERMIS
• PANNICULUS ADIPOSUS/ SUBCUTIS
• Insulating layer of Adipocytes
THANK YOU