Structure and Function Structure and Function of Human Skinof Human SkinLianjun ChenHuashan HospitalImportance of the study of skin diseasesl lCommon and prevalent diseasesl lSkin beauty and health carel lreflection of the body health（paraneoplastic skin diseases)l lSex Transmitted Disease(STD),AIDS,other contagious diseasesOUTLINEl lIntroduction of the Skinl lMicrostructure of the skinEpidermisEpidermisThe basement membrane zoneThe basement membrane zoneDermisDermisSubcutisSubcutisAppendageal StructureAppendageal Structurel lThe function of the skinIntroductionl lThe single biggest organ in the bodyl lCover an average area of 1.5 m2l lVarying thickness(0.4-4mm)l lDifferent color by the race,age,gender&locationl lPerform many vital roles Microstructure of the skinl lEpidermisl lDermisl lSubcutisl lThe basement membrane zonel lAppendageal StructureEpidermisl lDerived from ectoderm l lThe celluar external layerKeratinocytenon-keratinocyte l lMelanocyteMelanocytel lLangerhans cellLangerhans celll lMerkel cellMerkel cellKeratinocytesl l stratum basale,basal cell layerl l stratum spinosum,prickle cell layerl l stratum granulosum,granular layerl l stratum luciduml l stratum corneum,horny layerKeratohyaline Granules keratinocyte non-keratinocytekeratin +tonofilament +desmosome +dendritic-shaped +Function of the keratinocytesl lContinuously producing keratin and forming horny layer to protect against various chemical and physical factorsl lParticipating immune response in the skinl lSecreting cytokines and helping to activate T lymphocytes Desmosomel lAttachment plates between adjacent Attachment plates between adjacent keratinocytes in basal layer and prickle layerkeratinocytes in basal layer and prickle layer l lDesmosome transmembrane proteinDesmosome transmembrane protein desmoglein,DGdesmoglein,DG desmocollin,DCdesmocollin,DCl lDesmosome cytoplasm plakinDesmosome cytoplasm plakin desmoplakin,DPdesmoplakin,DP plakoglobulin,PGplakoglobulin,PG Non-keratinocytesl l Melanocytel l Langerhans celll l Merkel cellMelanocytesl lEpidermal melanin unit melanocytes are derived from the nerual melanocytes are derived from the nerual crest and reside in the basal layercrest and reside in the basal layerMelanocytes are dendritic cells and contain Melanocytes are dendritic cells and contain large number of melanosomeslarge number of melanosomes Any one melanocyte is contact with 30-40 Any one melanocyte is contact with 30-40 keratinocytes through its dendrites,form keratinocytes through its dendrites,form the so-called epidermal melanin unit.the so-called epidermal melanin unit.l lProtective barrier against UVLangerhans cellsl lLangerhans cells are originate in bone marrow.Langerhans cells are originate in bone marrow.They exist in the epidermis above the basal layer.They exist in the epidermis above the basal layer.l lThey are characterized by a folded nucleus and They are characterized by a folded nucleus and distinct intracytoplasmic organelles called distinct intracytoplasmic organelles called Birbeck Birbeck granulesgranules，resembling a tennis racquet.resembling a tennis racquet.l lRecognition,uptake,processing,and presentation Recognition,uptake,processing,and presentation of antigens to sensitized T lymphocytes.of antigens to sensitized T lymphocytes.Langerhans GranulesBirbeck granulesMerkel cellsl la kind of neurosecretory celll llocated directly above the basement membrane and closely associated with neurites,so called Merkel cell-axon complex.Basement membrane zonel lThe base of basal cellThe base of basal cell containing hemidesmosome containing hemidesmosomel lThe lamina lucidaThe lamina lucida A clear zone crossed by a fine network of anchoring A clear zone crossed by a fine network of anchoring filaments,largely composed of the structural protein filaments,largely composed of the structural protein lamininlamininl lThe lamina densaThe lamina densa An electron dense band,largely composed of type IV An electron dense band,largely composed of type IV collagencollagenl lThe reticular lamina(collagen VII)The reticular lamina(collagen VII)Dermisl lDerived from mesoderm l lPapillary dermis&reticular dermisl lConnective tissueCollagen,elastic fiber,reticulum fiberCollagen,elastic fiber,reticulum fiberl l matrix(mucopolysaccharides)l lblood vessel,lymphatics,nerve endingl lAppendageal sructure apocrine gland,eccrine gland,sebaceous apocrine gland,eccrine gland,sebaceous gland,hair follicle,nail,et algland,hair follicle,nail,et alSubcutisl lIt consist largely of fat tranversed by nerves and blood vessels.l lThe name implies that it is not properly the part of the skin,however,it could be an integrated whole as for the function.Appendagesl lHair folliclesl lSebaceous glandsl lSweat glandsEccine glandsEccine glandsApocrine glandsApocrine glandsl lNailsPilosebaceous unitsHair follicles l lClassificationTerminal hairTerminal hair Scalp,axillae,pubic,beard Scalp,axillae,pubic,beard eyebrow,eyelash,vibrissaeyebrow,eyelash,vibri