ppt on Anatomy of Skin.pptxdvhwjgdyuwgydgy

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1. BASIC SKIN STRUCTURE Dr.Talat Fathima Associate Professor Department Amraz e Jild Wa Tazeeniyat Tipu Sultan Unani Medical College and Hospital

2. Learning Objective At the end of the Session the student should able to explain the different layers of the skin and its functions .

3. INTEGUMENTARY SYSTEM In biology, integument is the natural covering of an organism or an organ, such as its skin, husk or shell. It derives from integumentum , which means ‘a covering’ in Latin and is an alternative name of skin. The integumentary system is an organ system consisting of the skin , hair , nails , and exocrine glands . Dermatology is the branch of medicine dealing with the skin, nails, hair and its diseases.

4. SKIN Largest organ of the body Completely covers the body approx 2 mt sq and having 7-12% of the total body weight Average thickness: 1-2 mm. ( 0.5mm eyelids, 6mm palms and soles) Renewal of skin takes place in 28-50 days by shedding of the outer layer . The thin layer of tissue forming the natural outer covering of the body of a person or animal . Skin is an organ because it consists of different tissues that are joined to perform a specific function.

5. FUNCTIONS OF SKIN 1. Protection - Physical barrier that protects underlying tissues from injury, UV light and bacterial invasion. - Mechanical barrier is part non specific immunity (skin, tears and saliva). 2. Regulation of Body T emperature - H igh temperature or strenuous exercise; sweat is evaporated from the skin surface to cool it down . - vasodilation (increases blood flow) and vasoconstriction (decrease in blood flow) regulates body temperature.

6. 3. Sensation - N erve endings and receptor cells that detect stimuli to temperature, pain, pressure and touch . 4. Excretion - S weat removes water and small amounts of salt, uric acid and ammonia from the body surface 5. Blood Reservoir - D ermis houses an extensive network of blood vessels carrying 8-10% of total blood flow in a resting adult. 6. Synthesis of Vitamin D ( cholecalciferol ) - UV rays in sunlight stimulate the production of Vit -D . Enzymes in the kidney and liver modify and convert to final form; calcitriol (most active form of Vit -D .) Calcitriol aids in absorption of calcium from foods and is considered a hormone .

7. SKIN STRUCTURE 3 layers of skin structure Epidermis Epithelial tissue Dermis Dense connective tissue proper ( irregular) Hypodermis Subcutaneous tissue (loose connective tissue proper and adipose tissue)

8. 3 LAYERS OF SKIN

9. EPIDERMIS Epidermis It i s avascular stratified squamous epithelium  N utrients and oxygen diffuse from capillaries in the dermis Cells of Epidermis Keratinocytes (90 %) : W aterproofs & protects skin, nails, hair, stratum corneum and also provides rigidity by producing tough, triple-helix-shaped protein strand called Keratin . Melanocytes (8 %) : Produce melanin that gives skin color Merkel Cells : Slowly adapting mechanoreceptors that mediate the senses of touch and hair movement . Langerhans ’ Cells : I mmunological defense

10. EPIDERMIS The structural relationship and interface between the epidermis and underlying dermis. The proportions of the various layers differ with the location sampled. Dermis Epidermis Epidermal ridge Dermal papilla

11. SKIN STRUCTURE: EPIDERMIS Thin Skin  Covers most of the body  Has four layers of keratinocytes Thick Skin  Covers the palms of the hands and soles of the feet  Has five layers of keratinocytes

12. SKIN STRUCTURE: EPIDERMIS  The five strata of keratinocytes in thick skin  From basal lamina to free surface Stratum Basale Stratum Spinosum Stratum Granulosum Stratum L ucidum (absent in thin skin) Stratum Corneum

13. Thick skin EPIDERMIS LAYER

14. SKIN STRUCTURE: EPIDERMIS Stratum Basale  It i s attached to basement membrane by hemidesmosomes  Forms a strong bond between epidermis and dermis  Forms epidermal ridges (e.g., fingerprints )  Dermal papillae (tiny mounds) Increase the area of basement membrane Strengthen attachment between epidermis and dermis  Has many basal cells or germinative cells .

15. It is the inner most single columnar stemcell layer that servers the regenrative function and proliferates to fill the skin defects Melanocytes which secrete melanin give the skin its color .

16. Thick skin SEM  25 Epidermal ridge Pores of sweat gland ducts Epidermal ridges

17. SKIN STRUCTURE: EPIDERMIS Stratum Spinosum the ‘spiny layer’ Produced by division of stratum basale  8-10 layers of keratinocytes bound by desmosomes  Continue to divide, increasing thickness of epithelium Contain dendritic (Langerhans) cells , active in immune response

18. SKIN STRUCTURE: EPIDERMIS Stratum Granulosum The ‘ grainular layer’ Stops dividing, starts producing keratin & keratohyalin Keratin A tough, fibrous protein Makes up hair and nails Keratohyalin Dense granules Cross-link keratin fibers

19. SKIN STRUCTURE: EPIDERMIS Stratum Lucidum The ‘clear layer’ Found only in thick skin (Palms & Soles) Covers stratum granulosum Stratum Corneum The ‘horn layer’ Exposed surface of skin 15 to 30 layers of keratinized cells Water resistant Shed and replaced every 2 weeks

20. Located between epidermis and subcutaneous layer Anchors epidermal accessory structures (hair follicles, sweat glands) Two components Outer papillary layer Deep reticular layer SKIN STRUCTURE: DERMIS DERMIS

21. SKIN STRUCTURE: DERMIS Papillary Layer  Consists of areolar tissue  Contains smaller capillaries, lymphatics, and sensory neurons and which supplies the epidermis with nutrients and plays an important role in temperature regulation  It is also responsible for fingerprints,gripping and sensing abilities Reticular Layer  Consists of dense irregular connective tissue  Contains larger blood vessels, lymphatic vessels, and nerve fibers and sweat glands,sebceousglands and roots of hair follicles  Contains collagen and elastic fibers

22. Hair Papillary layer Reticular layer Cutaneous plexus Papillary plexus Epidermal ridges Dermal papillae Capillary loop of papillary plexus DERMIS LAYER

23. SKIN STRUCTURE: HYPODERMIS Hypodermis (Subcutaneous Layer)  Lies below the integument  Stabilizes the skin  Allows separate movement  Made of elastic areolar and adipose tissues  Connected to the reticular layer of integument by connective tissue fibers Deposits of Subcutaneous Fat  Distribution patterns determined by hormones  Reduced by cosmetic liposuction ( lipoplasty )

24. SKIN STRUCTURE: HYPODERMIS

25. Thank YOU