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

1. STRUCTURE OF SKIN
Dr Aseem Sharma
Dermatology Resident

2. INTRODUCTION
• Surface Area 1.62/ 1.45 sq metres (M/F)
• 16 – 20% Body Weight (approx 5 kg)
• Largest Organ

3. TYPES OF SKIN
• 02 Types :
GLABROUS (Non-Hairy)
‘Dermatolglyphics’
NON-GLABROUS (Hair-bearing)

4. LAYERS OF THE SKIN
EPIDERMIS
CUTICLE/EPITHELIUM
DERMIS
HYPODERMIS/PANNICULUS ADIPOSUS
- SUBCUTIS

6. APPENDAGES OF THE SKIN
• Hair
• Nails
• Glands
1. Eccrine
2. Apocrine
3. Sebaceous

7. EMBRYOLOGY
SPECIFICATION : Commitment 0-2 months FL
MORPHOGENESIS: Specialization 2-5 months FL
DIFFERENTIATION: Maturation 5-9 months FL

8. 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

9. 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

10. 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

11. EMBRYOLOGY
• HYPODERMIS (MESENCHYME)
14 Weeks FL - Lipoblasts  Lipocytes

12. EPIDERMIS
• Stratified Squamous Epithelium
• Variable Thickness 0.4 – 1.5 mm
• Cellular Components :
95% Keratinocytes
5% Merkel, Melanocytes, Langerhans

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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

15. STRATUM SPINOSUM
• Prickle-Cell layer
• Desmosomes  Spines
• 8-10 cell layers, Nucleated
• Large, Flattened, Polyhedral cells

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STRATUM GRANULOSUM
• Intracellular Basophilic Keratohyaline granules
• 2-5 cell layer, Nucleated
• Odland Bodies/ Lamellar Granules – facilitate
desquamation

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STRATUM LUCIDUM
• Glabrous Skin only
• ‘Electron-Luscent’
• Nucleated, Transitional Cells

18. STRATUM CORNEUM
• Outermost Skin Layer
• 20-25 Cell layer
• Corneocytes - Enucleated, minus
Cytoplasmic Organelles, Terminally
Differentiated; ‘Soft Keratin’

19. 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

21. PAPILLARY DERMIS
• 1/10th of Dermis; Interdigitates with Epidermal
Rete Ridges.
• Small Diameter COLLAGEN Fibres
• OXYTALAN ELASTIC Fibres
• Higher Metabolic Rate; Loose Connective tissue

22. RETICULAR DERMIS
• 9/10th of Dermis; Merges with Underlying
Subcutaneous Fat
• Large Diameter COLLAGEN Fibres
• ELAUNIN ELASTIC Fibres
• Densely-packed Connective Tissue

23. COMPONENTS OF DERMIS
ACELLULAR (MAJOR COMP)
GROUND MATRIX
CONNECTIVE TISSUE MATRIX
(Collagen/Elastin)
CELLULAR
FIBROBLASTS
MACROPHAGES/MONOCYTES/DENDROCYTES
MAST CELLS

24. 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

25. GROUND SUBSTANCE
PGs
Chondroitin Sulfates
Dermatan Sulfates
Heparan Sulfates
GAGs
Hyaluronan

26. 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

27. ULTRASTRUCTURE COLLAGEN
• Triple Helical Conformation
• (Glycine-X-Y) X - Proline
Y - Hydroxyproline
Glycosylated  Interchain Bonding  Secreted
 Cleaved  Cross-Linked

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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

29. HYPODERMIS
• PANNICULUS ADIPOSUS/ SUBCUTIS
• Insulating layer of Adipocytes

30. THANK YOU