Structure and Structure and

Function of Human Function of Human

SkinSkin

Structure and Structure and

Function of Human Function of Human

SkinSkinLianjun ChenLianjun Chen

Huashan HospitalHuashan Hospital

Importance of the Importance of the study of skin diseasesstudy of skin diseases Common and prevalent diseasesCommon and prevalent diseases Skin beauty and health careSkin beauty and health care reflection of the body health （paraneoplastic skin diseases)

Sex Transmitted Disease(STD), Sex Transmitted Disease(STD), AIDS, other contagious diseasesAIDS, other contagious diseases

OUTLINEOUTLINE

Introduction of the SkinIntroduction of the Skin Microstructure of the skinMicrostructure of the skin

– EpidermisEpidermis– The basement membrane zoneThe basement membrane zone– DermisDermis– SubcutisSubcutis– Appendageal StructureAppendageal Structure

The function of the skinThe function of the skin

IntroductionIntroduction

The single biggest organ in the bodyThe single biggest organ in the body Cover an average area of 1.5 mCover an average area of 1.5 m22

Varying thickness (0.4-4mm)Varying thickness (0.4-4mm) Different color by the race, age, Different color by the race, age,

gender & locationgender & location Perform many vital roles Perform many vital roles

Microstructure of the Microstructure of the skinskin

EpidermisEpidermis DermisDermis SubcutisSubcutis

The basement membrane zoneThe basement membrane zone Appendageal StructureAppendageal Structure

EpidermisEpidermis

Derived from ectoderm Derived from ectoderm The celluar external layerThe celluar external layer

– KeratinocyteKeratinocyte– non-keratinocyte non-keratinocyte

MelanocyteMelanocyte Langerhans’ cellLangerhans’ cell Merkel cellMerkel cell

KeratinocytesKeratinocytes

stratum basalum, basal cell layerstratum basalum, basal cell layer stratum spinosum, prickle cell stratum spinosum, prickle cell

layerlayer stratum granulosum, granular stratum granulosum, granular

layerlayer stratum lucidumstratum lucidum stratum corneum, horny layerstratum corneum, horny layer

keratinocyte non-keratinocyte

keratin + ─

tonofilament + ─

desmosome + ─

dendritic-shaped ─ +

Function of the Function of the keratinocyteskeratinocytes

Continuously producing keratin Continuously producing keratin and forming horny layer to and forming horny layer to protect against various chemical protect against various chemical and physical factorsand physical factors

Participating immune response in Participating immune response in the skinthe skin

Secreting cytokines and helping to Secreting cytokines and helping to activate T lymphocytesactivate T lymphocytes

DesmosomeDesmosome

Attachment plates between adjacent Attachment plates between adjacent

keratinocytes in basal layer and keratinocytes in basal layer and

prickle layerprickle layer Desmosome transmembrane proteinDesmosome transmembrane protein

– desmoglein,DGdesmoglein,DG

– desmocollin,DCdesmocollin,DC

Desmosome cytoplasm plakinDesmosome cytoplasm plakin– desmoplakin,DPdesmoplakin,DP

– plakoglobulin,PGplakoglobulin,PG

Non-keratinocytesNon-keratinocytes

MelanocyteMelanocyte

Langerhans cellLangerhans cell

Merkel cellMerkel cell

MelanocytesMelanocytes

Epidermal melanin unit Epidermal 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 layer– Melanocytes are dendritic cells and Melanocytes are dendritic cells and

contain large number of melanosomescontain large number of melanosomes– Any one melanocyte is contact with 30-Any one melanocyte is contact with 30-

40 keratinocytes through its dendrites, 40 keratinocytes through its dendrites, form the so-called epidermal melanin form the so-called epidermal melanin unit.unit.

Protective barrier against UVProtective barrier against UV

Langerhans’ cellsLangerhans’ cells

Langerhans’ cells are originate in bone marrow. Langerhans’ cells are originate in bone marrow.

They exist in the epidermis above the basal They exist in the epidermis above the basal

layer .layer .

They are characterized by a folded nucleus and They are characterized by a folded nucleus and

distinct intracytoplasmic organelles called distinct intracytoplasmic organelles called

Birbeck granulesBirbeck granules ，， resembling a tennis racquet.resembling a tennis racquet.

Recognition, uptake, processing, and Recognition, uptake, processing, and

presentation of antigens to sensitized T presentation of antigens to sensitized T

lymphocytes.lymphocytes.

Langerhans’ Granules

Birbeck granules

Merkel cellsMerkel cells

a kind of neurosecretory cella kind of neurosecretory cell located directly above the located directly above the

basement membrane and basement membrane and closely associated with closely associated with neurites, so called neurites, so called Merkel cell-Merkel cell-axon complexaxon complex..

Basement membrane Basement membrane zonezone

The base of basal cellThe base of basal cell

containing hemidesmosomecontaining hemidesmosome The lamina lucidaThe lamina lucida

– A clear zone crossed by a fine network of A clear zone crossed by a fine network of anchoring filaments, largely composed of the anchoring filaments, largely composed of the structural protein lamininstructural protein laminin

The lamina densaThe lamina densa– An electron dense band, largely composed of An electron dense band, largely composed of

type IV collagentype IV collagen The reticular lamina(collagen VII)The reticular lamina(collagen VII)

DermisDermis Derived from mesoderm Derived from mesoderm Papillary dermis & reticular dermisPapillary dermis & reticular dermis Connective tissueConnective tissue

– Collagen, elastic fiber, reticulum fiberCollagen, elastic fiber, reticulum fiber matrix (mucopolysaccharides)matrix (mucopolysaccharides) blood vessel, lymphatics, nerve endingblood vessel, lymphatics, nerve ending Appendageal sructureAppendageal sructure

– apocrine gland, eccrine gland, sebaceous apocrine gland, eccrine gland, sebaceous gland, hair follicle, nail, et algland, hair follicle, nail, et al

SubcutisSubcutis

It consist largely of fat tranversed It consist largely of fat tranversed by nerves and blood vessels.by nerves and blood vessels.

The name implies that it is not The name implies that it is not properly the part of the skin, properly the part of the skin, however, it could be an integrated however, it could be an integrated whole as for the function.whole as for the function.

AppendagesAppendages

Hair folliclesHair follicles

Sebaceous glandsSebaceous glands

Sweat glandsSweat glands

– Eccine glandsEccine glands

– Apocrine glandsApocrine glands

NailsNails

Pilosebaceous units

Hair follicles Hair follicles

ClassificationClassification– Terminal hairTerminal hair

Scalp,axillae, pubic,beard Scalp,axillae, pubic,beard eyebrow,eyelash,vibrissaeyebrow,eyelash,vibrissa

– VellusVellus– lanugolanugo

Hair AnatomyHair Anatomy

Infundibulum – surface to entrance Infundibulum – surface to entrance of sebaceous ductof sebaceous duct

Isthmus – sebaceous duct to pilar Isthmus – sebaceous duct to pilar muscle insertionmuscle insertion

Lower segment Lower segment

–– Stem,Bulb (matrix and papilla)Stem,Bulb (matrix and papilla) Perifollicular sheath (mesenchyme)Perifollicular sheath (mesenchyme)

Arrector pili muscle

Infundibulum

Isthmus

Stem

Bulb

anagen catagen telogen

Sebaceous glandsSebaceous glands Distribute throughout all skin sites Distribute throughout all skin sites

except palms and solesexcept palms and soles ，， greatest greatest abundant on scalp, face,middle part of abundant on scalp, face,middle part of the body and vulvae.the body and vulvae.

Always associated with upper portion of Always associated with upper portion of the hair folliclesthe hair follicles

Reach skin surface,such as Reach skin surface,such as – vermilion border of the lip(Fordyce’s spotsvermilion border of the lip(Fordyce’s spots））– areolas(Montgomery’s tubercles)areolas(Montgomery’s tubercles)– prepuce(Tyson’s glands) prepuce(Tyson’s glands) – eyelids(Meibomian’s glands)eyelids(Meibomian’s glands) Production of sebumProduction of sebum

Eccrine glandsEccrine glands Distribution: almost all skin siteDistribution: almost all skin site

– Exclude the vermilion border of the Exclude the vermilion border of the lip, nympha, phallus, glans, flexion lip, nympha, phallus, glans, flexion side of prepuce and nail bedsside of prepuce and nail beds

– most abundant on the palms, soles most abundant on the palms, soles and axillaeand axillae

Reach to skin surface directlyReach to skin surface directly

Under psychological and thermal Under psychological and thermal

control control

Eccrine glandsEccrine glands Composition of the eccrine glandComposition of the eccrine gland

– Coil gland is composed of a single Coil gland is composed of a single layer of cells with two types: pale layer of cells with two types: pale cell and darker-staining cell and cell and darker-staining cell and regulated by cholinergic nerveregulated by cholinergic nerve

– The duct is composed of a double The duct is composed of a double layer of basophilic epithelial cells layer of basophilic epithelial cells and divided into intraepidermal and divided into intraepidermal component and intradermal component and intradermal componentcomponent

•：⑴

Function of the eccrine Function of the eccrine glandgland

Dissipate excessive body heatDissipate excessive body heat

Soften horninessSoften horniness

Acidify sweatAcidify sweat

Take place of partial renal functionTake place of partial renal function

Emulsify lipidEmulsify lipid

Secrete immunoglobulinSecrete immunoglobulin

Apocrine glandsApocrine glands

Distribution: generally confined to Distribution: generally confined to axillae, areolae and the anogenital axillae, areolae and the anogenital region.region.

reach to the hair follicle instead of skin reach to the hair follicle instead of skin surfacesurface

Becoming active at pubertyBecoming active at puberty Producing a protein-rich secretion , Producing a protein-rich secretion ,

sometimes gives out a characteristic sometimes gives out a characteristic odour. odour.

NailsNails

Consist of a dense plate of hardened Consist of a dense plate of hardened keratin between 0.3 and 0.5mm thickkeratin between 0.3 and 0.5mm thick

The nail is made up of a nail bed, nail The nail is made up of a nail bed, nail matrix and a nail plate. matrix and a nail plate.

The thickened epidermis which underlies The thickened epidermis which underlies the free margin of the nail at the the free margin of the nail at the proximal end is called the hyponychium. proximal end is called the hyponychium.

Fingernails grow at 0.1 mm per day; the Fingernails grow at 0.1 mm per day; the toenails more slowly.toenails more slowly.

Skin is the largest organ in the body by Skin is the largest organ in the body by weight and surface area.weight and surface area.

Skin is composed by three layers : Skin is composed by three layers : epidermis , dermis and subcutis.epidermis , dermis and subcutis.

Epidermis is the outer layer composed Epidermis is the outer layer composed mainly of keratinocytes but also mainly of keratinocytes but also melannocytes and Langerhan’s cells.melannocytes and Langerhan’s cells.

Dermis is a supportive connective tissue Dermis is a supportive connective tissue layer comprised mainly of collogen but layer comprised mainly of collogen but also containing elastin embbed in a also containing elastin embbed in a matrix of mucopolysaccharides.matrix of mucopolysaccharides.

Hairs are ketatinized tubes emerging from Hairs are ketatinized tubes emerging from invaginations of the epidermis called follicles.invaginations of the epidermis called follicles.

Sebaceous glands deliver sebum into follicle Sebaceous glands deliver sebum into follicle lubricating the hair surface.lubricating the hair surface.

Eccrine sweat glands are found almost over Eccrine sweat glands are found almost over the entire skin surface and innervated by the the entire skin surface and innervated by the sympathetic nervous system,responding to sympathetic nervous system,responding to temperature/psychological changes.temperature/psychological changes.

Apocrine sweat glands are localized (axillae, Apocrine sweat glands are localized (axillae, nipples,perineum,scalp) and androgen-nipples,perineum,scalp) and androgen-sensitive.sensitive.

Nails, like hair, are made largely of keratin. Nails, like hair, are made largely of keratin.

Function of the skinFunction of the skin As a barrierAs a barrier

– Provides a protective barrier to: Provides a protective barrier to: mechanical,thermal,and other physical mechanical,thermal,and other physical

injuryinjury the ingress of noxious agentsthe ingress of noxious agents the excessive loss of moisture and protein(if the excessive loss of moisture and protein(if

the skin absent or seriously compromised)the skin absent or seriously compromised) The harmful effect of ionizing radiationThe harmful effect of ionizing radiation

especially ultraviolet radiatioespecially ultraviolet radiatioSensationSensation

– Rich in nerve ending and specialized sensory Rich in nerve ending and specialized sensory receptorreceptor

Function of the skinFunction of the skin ThermoregulationThermoregulation

– Skin is the principle organ of heat controlSkin is the principle organ of heat control Immunological surveillance Immunological surveillance

– Contains immunologically component cellsContains immunologically component cells Biochemical reactionBiochemical reaction

– Vitamin D synthesis Vitamin D synthesis – Involved in androgen degradation and Involved in androgen degradation and

othersothers Social and sexcial communicationSocial and sexcial communication

– Disorders of the skin such as dicoloration Disorders of the skin such as dicoloration may cause tremendous stress of human, may cause tremendous stress of human, impair the individual’s sense of well-being impair the individual’s sense of well-being and self-worth.and self-worth.

Some pictures are from Some pictures are from Mosby’s Color Mosby’s Color Atlas and Textbook of Dermatology. Atlas and Textbook of Dermatology. These cannot be copied without the These cannot be copied without the pemission of the publisher, only used in pemission of the publisher, only used in self-learning.self-learning.

Web address of this curriculumWeb address of this curriculum

http://jpkc.fudan.edu.cn/s/283/main.jspy From 12th .Oct, practice timeFrom 12th .Oct, practice time

– Place of Assembly: dermatopathology Place of Assembly: dermatopathology Unit, floor 3, building 6, Huashan Unit, floor 3, building 6, Huashan Hospital Hospital

– Time of Assembly: 1:30 p.m.Time of Assembly: 1:30 p.m. Tel: 13817311071 Lianjun ChenTel: 13817311071 Lianjun Chen