Presentation on theme: "Anatomy, Function of Human Skin and Diagnosis"— Presentation transcript:
1 Anatomy, Function of Human Skin and Diagnosis Dr . Ali elethawiSpecialist dermatologistC.A.B.D ,F .I .C.M.S
2 The integumentary system is synonymous with: The integumentary system is synonymous with:The skin and its appendages :sweat glands, nails, hair, sebaceous glands & arrector pili muscles.Mammary glandsTeeth
3 The skin:is the interface (surface) between human & environmentlargest organ in the body: 16% of our body weight ≈ 4kgIts surface area is of m2
4 skin layers: Skin has three layers: 1.The epidermis, the outermost layer of skin, provides a waterproof barrier and creates our skin tone.2.The dermis; beneath the epidermis, major structural elementThree types of components (cellular, fibrous matrix, diffuse and filamentous matrix).Also site of vascular ,lymphatic, and nerve networks.3.The subcutaneous tissue (hypodermis):is made of fat and connective tissue.
9 skin can be classified as thick or thin: 1) Thick skin- covers palms and soles,- has sweat glands, but lacks hair follicles, arrector pili muscles, and sebaceous glands2) Thin skin- covers most of the rest of the body- contains sweat glands & hair follicles, arrector pili muscles, and sebaceous glands.skin can also be classified as hairy &non hairy1.Non hairy skin: Lip, glans penis, labia minora, palms, soles2.hairy skin : covers most of the rest of the body
11 Epidermis: It is stratifed squamous epithelium epithelium thickness vary from 0.05mm in eyelids to 1.8 mm in palm & soleupper layers dead, filled with keratin (waxy protein)lower layers living cellsavascular( No blood vessels)replaced every days (i.e: Transit time: is the time needed for cell maturation from basal layer to the surface, normally = days)
13 Layers of epidermis 1. Basal layer ( stratum basalis): single layer of columnar cellsdeepest layer,Actively dividing cells : In normal skin 30% of basal cells are preparingfor division (growth fraction)only cells that get adequate nutrition and oxygen by diffusion from tissues belowbordered below by basement membrane : hemidesmosomes attachedthem to underlying lamina densa of BMZ
14 2. Spinous (prickle) cell layer: 7-9 layers of cells keratinocytes larger than basal layer.Keratinocytes firmly attached bycytoplasmic process (desmosomes) &intercellular glycoprotein cementTonofilaments are small fibers running from cytoplasm to desmosomes
15 3. Granular layer: 2-3 layers Cells flatter than spinous layer, Contain irregular basophilic granules of keratohyalin .Cells flatter than spinous layer,No nucleusNo intracytoplasmic organellesMore tonofibrilsas cells move up from s. basale they die & get flatterand thinnerkeratinization begins here
16 4. Stratum Luidum: Thin translucent band. Only in palms & soles 5. Stratum corneum: SC:Made of many layers of flattened dead cells (corneocytes),has no nuclei or cytoplasmic organelles.like Bricks-stuck together by intercellular lipidswater resistant
23 Cells of epidermis1. keratinocytes : most (80%) cells in epidermis synthesize keratin2. melanocytes : found in the deepest layer synthesize melanin pigment.3. Merkel cells : touch receptors, attached to nerve cell4. dentritic cells(Langerhans cells) : found in st. spinosumand st. granulosum are : if detected antigen they alert immune system (antigen presenting cell)5.stem cells : undifferentiated cells found only in deepest layer
24 basement membrane zone the basement membrane lies between epidermis & dermisComposed of:Hemidesmosomes of the basal layer ; attach to lamina densa of BMZLamina Lucida: is electron lucent area lies below basal cell layer.Lamina Densa : Fine anchoring filaments cross lamina lucida & connect lamina densa of plasma membrane of basal cell layer.Anchoring fibrils, :extend from deep part of lamina densa to papillary dermis Function :Provide mechanical supportEncouraging adhesion, growth, differentiation & migration of overlying basal cellsAct as semipermeable filter that regulate transfer of nutrients & cells between dermis & epidermis
26 Dermis: gel-like matrix Lies between epidermis & subcut. Fat strong, flexible, connective tissue gives skin its strength and resilienceSupport epidermis structurally & nutritionallyIt contain cells ,fiber , ground substance, nerves endings, muscles, skin appendages , lymphatic vessels and blood vessels .LAYERS OF DERMIS; structurally divided into two areas:1. Papillary layer : a superficial thin area adjacent to the epidermis,. mainly areolar connective tissue , dermal papillae (capillary loops ,sensory cells)2. reticular layer :a deep thicker area. mainly dense (irregular connective tissue)dermal tearing = stretch marks.Dermis Interdigitate with epidermis.Dermal papillae is upward projection of dermisRete ridges: is the downward ridges of epidermisThis allow adhesion between dermis & epidermis as it increases the surface area between them
29 Cells of dermis The dermis is composed of three major types of cells: Fibroblasts.Macrophages.Adipocytes.
30 fibers of dermis Collagen fibers: make 70-80% of dermis dry weight Compose of thinner fibrils packed in bundlesMade of 3 polypeptide chains; (proline, hydroxyproline, glycin)Its tensile strength prevent tearing when skin is stretched.Elastic fibers:2% of dermis dry weightelastin is made up of polypeptides rich in glycine, desmosine, valineHave amorphous elastin core surrounded by elastic tissue micrifibrillar componentReticular fibers: fine collagen fiber found in fetal skin , adult skin appendages& around bl.v.
31 Ground substance of dermis Composed ofglycosaminoglycan (hyaluronic acid & dermatan sulphate) with smaller amount of heparan sulphate & chondroitin sulphateFunctions:allowing nutrients, hormones & waste products to pass through dermisActs as lubricants between fibersProvides bulk act as shock absorber
32 Muscles Smooth arrector pili muscle 1- sebum expression 2- goose pimples from cold,3- nipple erectionsmooth dartos muscle ;raising of scrotumStriated fibers (platysma) & some of muscles of facial expression found in dermis
33 Blood vessels 2 main horizontal plexus, superficial & deep Under sympathetic nervous control .Regulate body temperature
34 Nerves One million nerve fibers mostly in the face & extremities Both mylinated & unmyelinated fibers existItch is follow stimulation of free nerve endings close to dermo-epidermal junction
35 Hypodermis( subcutaneous tissue). lies below the dermis.attach the skin to underlying bone and muscleas well as supplying it with blood vessels and nerves.It consists of loose connective tissue and elastin.The cells are: adipocytes (main cell ;the hypodermis contains 50% of body fat) ,fibroblasts& macrophagesFat serves as padding and insulation for the body.
37 The Physiology of SkinThe skin is a metabolically active organ with vital functions such as protection and homeostasis.
38 Functions of the skin1.Provides a protective barrier against mechanical, thermal and physical injury and noxious agents.2.Prevents loss of moisture.3. UV protection Reduces the harmful effects of UV radiation.4.Acts as a sensory organ.5. Thermoregulation ,helps regulate temperature control.6.Plays a role in immunological surveillance.7. Synthesizes vitamin D3 (cholecalciferol).8.Has cosmetic, social and sexual associations.
40 Sweat Glands Eccrine glands Sweat Glands ~3 Million total on skin, ~3000 sweat glands/inch2most numerous on palms, soles, forehead, armpitsessentially a tiny coiled tube that opens to skin surfacesecret sweat ; helps maintain temperature and fluid/electrolyte balancestimulated by heat ‡ sweat ‡ evaporative coolingApocrine sweat glandsmuch less common, modified sweat glandsconfined to axillary and genital areatheir ducts open into hair folliclessecretions contain fatty acids and proteins in addition to “sweat”respond especially to stress and sexual stimulation
41 Skin Glands Sebaceous Glands( Oil glands , holocrine) 2 or more per hair folliclesecrete sebum = breakdown products of dead cells.keeps hair soft and pliable esp. on face and scalpNot found on palms, soles or dorsal side of feetreduces heat losslipids are poor heat conductors ----helps prevent water evaporationbecome active at puberty ‡ acne
44 Hairthe hair on the scalp does protect us from UV radiation and minor injury.But today, the hair is of cosmetic value.Hair follicle form before nine week of fetal life when hair germ grows obliquely down into dermis.Types of hair: 1- Lanugo hair Vellus hair 3- Terminal hairHair growth (Hair cycle) is cyclical and has 3 phases: anagen, catagen & telogen
45 NailsHard keratin of nail plate formed in nail matrix which lies in an invagination of epidermis on back of terminal phalanx of digits toesIt provide strength & protection for terminal phalanx & allow handling of fine objectsFinger nail growth is mm per weekSlower in toe nailsFaster growth in summer
46 The epidermis is from surface ectoderm. Skin Embryology:Origins of the Integumentary System: (The Skin)The epidermis is from surface ectoderm.The dermis is derived from mesoderm.
47 Hair: A hair follicle develops as a proliferation of the epidermal stratum germinativum and extends into the underlying mesenchyme.Nails: develop from thickened areas of epidermis at the tips of each digit called nail fields.Later these nail fields migrate onto the dorsal surface surrounded laterally and proximally by folds of epidermis called nail folds
48 Both the sebaceous glands and sweat glands ( mammary glands) are derived from the epidermis and grow downwards into the dermis.The majority of sebaceous glands originate as buds from developinghair follicle root sheath.Sebaceous glands in the glans penis and labia minora (independent of hair follicles) develop similarly, but as buds from the epidermis.
49 Must be distinguished from secondary or induced lesions 1- Primary Lesions( basic): are the first to appear and are due to the disease or abnormal state. Must be distinguished from secondary or induced lesionsMacule-patchesPapule- PlaqueNodule- TumorPurpura -Petechiae –Ecchymosis- HaematomaWhealVesicle-bullaCystPustule- abscessInfarctTelangiectasia, Erythema, Angiodema, Burrow, Comedo & Poikiloderma
50 Macule (Latin: macula, “spot”) < 5mm is a circumscribed area of change in skin color without elevation or depressionMacule < 5mmpatches > 5mm
51 Erythema: is redness caused by vascular dilatation
52 Papule: is a superficial, elevated, solid lesion, generally <0 Papule: is a superficial, elevated, solid lesion, generally <0.5 cm in diameter
53 Plaque A solid lesion more than 0.5 cm in diameter, often formed by the confluence is a plateau-like elevation above the skin surface
54 NoduleA circumscribed, elevated, solid lesion, Larger than papules: > 5 mm diameter (in both depth & width)tumor :Large nodule
55 Vesicle-Bulla ( Blister ) is a circumscribed elevated, superficial cavity containing fluid A vesicle <0.5 cmA bulla >0.5 cm
56 pustuleis a circumscribed, superficial cavity of the skin that contains a purulent exudate
57 Abscess: localized collection of puss more than 1 cm in diameter
58 Wheal: elevated, transitory, compressible papule or plaque produced by dermal edema
59 Angiodema: is diffuse swelling caused by subcutaneous oedema
60 Cyst: an epithelial lined cavity containing liquid or semisolid material (fluid, cells, and cell products)