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Structure and Functions of Skin PowerPoint Presentation

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Description : Check out this medical presentation on Anatomy of the Skin, which is titled "Structure & Functions of Skin", to know about dermatology, the branch of medicine concerned with the diagnosis and treatment of skin disorders. Know about structure and functions of skin.

Tags : Anatomy, Skin, Structure, Functions, dermatology, skin disorders

Published on : Jul 05, 2021 | Views : 3244 | Downloads : 8

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Slide 1-

Structure & Functions of Skin Dr N. K. Kansal Associate Professor
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Dermatology Dermatology – defined as ‘the branch of medicine concerned with the diagnosis & treatment of skin disorders’ However, dermatologists do not confine themselves purely to a study of intrinsic disorders of the skin Must also study internal medicine & the many environmental & occupational factors that so frequently cause skin problems
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Dermatology Probably at least 2000 different skin conditions might present to the dermatologist; vary enormously in severity Range from cosmetic problems, e.g., dry skin or wrinkles, through a huge variety of acute or chronic diseases - disfiguring, itchy or painful, less commonly fatal to life-threatening conditions Certain diseases, if untreated, may prove fatal within days (e.g., toxic epidermal necrolysis), weeks (e.g., pemphigus), months (e.g., malignant melanoma) or years (e.g., mycosis fungoides)
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Dermatology The patterns of dermatological diseases / disorders vary from one country to another Even in the same city the work of dermatologists differ, depending on their particular interests & expertise & on the social mix of their patients
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Dermatology Largest organ of the body In a 70 - kg person: skin wt- >5 kg; SA = 2 m2 Consists of a stratified, cellular epidermis & an underlying dermis of connective tissue Epidermis is mainly composed of keratinocytes & is typically 0.05 – 0.1 mm in thickness, up to 1.5 mm in palms & soles
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Layers of Skin Epidermis: Stratum basale (germinativum) Stratum spinosum Stratum granulosum Stratum lucidum (palms, soles) Stratum corneum (Malphigian layer = basal + spinous layers) Dermis: Papillary dermis Reticular dermis Subcutaneous Fat
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HPE Skin - forearm – very thin epidermis
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HPE – Palm – stratum lucidum
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Different Types of Cells in Epidermis Keratinocyte Melanocyte Langerhans’ cell Merkel cell
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Strata (layers) of Epidermis Stratum basale: Columnar / cuboidal cells; large oval nuclei, dense basophilic cytoplasm Stratum spinosum (spinous / prickle cell layer): Polygonal cells with delicate processes, desmosomes connect adjacent keratinocytes Stratum granulosum: Flattened diamond-shaped cells filled with coarse basophilic ‘keratohyaline’ granules
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Strata of Epidermis Stratum lucidum : Clear layer found in palms and soles, cells are nucleated, sometimes k/a transitional cells Stratum corneum : Flat, non-nucleated, eosinophilic layer; cells k/a corneocytes Dead layer shed during epidermal turnover
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Epidermal turnover/ transit time: Time taken for a cell to pass from basal layer to surface of skin Apprx. 40 – 56 days (normal skin)
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Melanocyte Neural crest derived cells Dendritic arborizing cells that synthesize and secrete melanin containing organelles called melanosomes Located in basal layer; 1:10 ratio Epidermal-Melanin Unit: A single melanocyte supplies melanosomes to 36 keratinocytes (1:36) Melanosomes vary in number and size according to skin type  differing skin color
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Melanocytes in culture
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Melanocyte Function of melanin - Impart colour to skin and hair - Protect the skin from UV radiation - Biochemical neutralizer of toxic, free radical oxygen derivatives Melanin: Eumelanin (brown / black) & phaeomelanin (yellow / red)
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Langerhans’ cell & Merkel cell Langerhans’ cell Type of macrophage, APCs Originate from bone marrow (mesodermal in origin) - Role in various immune processes like allergic contact dermatitis, immune tolerance, surveillance against neoplasia
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Merkel cell also k/a Merkel-Ranvier cell: Oval receptor cells Probably derived from keratinocytes Associated with sensation of light touch discrimination of shapes & textures
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Dermis Papillary dermis – A thin zone which lies beneath the epidermis Reticular dermis - thick zone which extends from base of papillary dermis to the surface of subcutaneous fat
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Structure of dermis Mainly non-cellular connective tissue Constituted of collagen, elastic fibers & ground substance (mucopolysaccharides, chondroitin sulphate & glycoproteins) Embedded nerves, blood vessels / capillaries, lymphatics, muscles & pilosebaceous, apocrine & eccrine units Cellular contents include fibroblasts, mast cells, histiocytes, Langerhans’ cells, lymphocytes & eosinophils
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Variation in thickness of skin Difference of thickness of the skin is dependent largely on dermal thickness, with the palms and soles being thickest (about 1.5 mm) & thinnest in the eyelids & post-auricular region (about 0.05 mm) Children & elderly have thinner skin than adults Males have thicker skin than females
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Hair Hair - a keratinized product of the hair follicle, a tube-like structure continuous with the epidermis at its upper end Present all over the skin except on vermillion of lips, palms, soles & skin of nail folds
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Types of hair Types of hair: 1) Lanugo (fine, soft, unpigmented; seen in utero- shed in 8th-9th month of gestation) 2) Vellus (soft) 3) Terminal (longer, coarse, pigmented) Also intermediate After puberty : secondary sexual terminal hair
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Hair Cycle Hair follicles undergo a repetitive sequence of growth & rest called the hair cycle Period of active hair growth is Anagen. Duration of this phase decides the length of hair; In humans, it is maximum on scalp Catagen is the regressive phase in which the follicular activity declines & ceases The hair stays in the Telogen (resting) phase till the beginning of next anagen phase
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Sebaceous Glands Lipid producing holocrine glands Arise from the hair follicle at the junction of the infundibulum & the isthmus Distributed all over the body except the palms & soles; most numerous, large and productive over the face & scalp Mature at puberty are stimulated by various hormones Major components of sebum: Triglycerides, wax esters, squalene, cholesterol esters & cholesterol
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Nail
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Nail Growth
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Functions of nails Help to grasp & manipulate objects Help in ‘pincer grip’ Protect terminal phalanx & fingertip Serve an aesthetic & cosmetic purpose
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Functions of Skin Barrier function Permeability Maintenance of fluid & electrolyte balance Thermoregulation- sweating Pigmentation Immune function Sensory receptor Endocrine function: Vitamin D synthesis
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Thank you!