Basic_anatomical_structure_of_skin_part_I_13_7_2024_Final-.pdf

Basic anatomical structure of skin- part-I Prof: Hamida Aldwibe Prof of D & V- 2024  The Skin  Is The largest organ of the body  Accounts for:  16 - 20 % of total body wt  Wet wt of adult male can be as heavy as:  4 kg (10-12 Ibs)  It has surfac...

Basic anatomical structure of skin- part-I Prof: Hamida Aldwibe Prof of D & V- 2024  The Skin  Is The largest organ of the body  Accounts for:  16 - 20 % of total body wt  Wet wt of adult male can be as heavy as:  4 kg (10-12 Ibs)  It has surface area of:  1.5 - 2 m2  Approximately 18-22 sq.ft Prof: Hamida Aldwibe-2024  The Skin Ihe  Receive approximately: Hair shaft— Receïve opproxïmotely: Dermal papillae One third of circulating E idermis  One thïrd cïrculotïng ’ Papillary S bpapiliary vascular" plexus blood volume. layer Pore Appendages ofski  Can Con be be nourished via nourïshed vio Reticular layer / t' Eccrine sweat gland Arrector pili muscle perfusion peRusion&& topïcolly. topically. Sebaceous (oil) gland Hair follicle ÜüÏf f0Ot Skin the mirror mïrror of ,‘/,iypodermis  Skïn is the of "tuperfisial fascia) internal diseases ïnternol dïseoses ffiervous structures Sensory nerve fiber Dermal vascular plexus Lamellar (Pacinian) corpuscle Prof: Hamida A/dwiöe-2024 Aldwibe-2024  Integumentary system  The skin & its appendages: Epiderm  1-Hair Papiiiary —L.z ›.  2-Sebaceous gland  3-Sweat glands  4- Nails  together are called: Prof: Hamida Aldwibe-2024  TRRT U S ST - PfsyadsM prwtnu0âozs from ezwIro«zmezztnI hands Ttsarwsonngulet0on senaory In3&zmut0o«s Coordksatlon of' Immune response $o paUsogezsa azszg unncora InKlein Skin = Cutaneous Appendages Produce fret's that Maoist Ozs Profane anM - Conzz'olc skin pro€nct mkull ttsnrwsorsgulwtton support tlpa ProMuoss fsaira Msst offs re provide delicate - Lubzlcata RETtCU RLA'FER touch ea«soatfons on Nozsrtatzom anM Restr6cN sprsaM of general body aurfoos cup$>o«ta epldormN pettsopsnc psnwb'ating vitamin Dy ep4dsrmlo &toras lipid zsesrves &f?acfsso ogtln to anM temperature dea Masuea Sebaceous gland Metact touch. praasurs. - Coordlnmzns kzsmune jznln, vibration, and pattsogono and tezzspszaturs mkln uanonra - Vbsaol assist in Use«wzozagugatlon Prof: Hamida A/dwi6e-2024 Aldwibe-2024  Multiple Morula which contain inner Zygote cell mass in the center Blastocyst  Embryology of the skin Skin structures derived Ectoderm from two of three forms primary germ layers: exoskeleton - Ectoderm - Mesoderm  Skin structures Skin structures derived from two derived from two of three ofthree primary primory germ germ layers foyers (ect/meso/endo): (ect/meso/endo): A) Ectoderm B) Mesoderm  Epidermis  Dermis Adnexal structures including:  Adnexol  Fibroblasts, Fibroblosts, fibrocytes  Folliculo-sebaceous Folliculo-seboceous unit (HF, seb.  Langerhans Longerhons cells G) G)  Blood Blood&& Lymph vessels  (except (except dermal dermol papilla: popillo:  Inflammatory lnflommotory Cells Cells mesenchymal structure (from mesenchymol structure (from (Macrophages, (Mocrophoges, mastmost cells) cells) embryonic embryonic mesoderm) mesoderm)  Muscles  Eccrine sweat & apocrine. Eccrine sweot& opocrine.GG  Adipocytes  Nail Noil unit Prof: Hamida A/dwi6e-2024 Aldwibe-2024  C.) Neuro-ectoderm:  Melanocytes (Neural creast)  Merkle cells (Neural creast)  Nerves  Specialized sensory receptors Prof: Hamida Aldwibe-2024  First trimester ~3–4 wks Single simple cuboidal epith ( layer of ectoderm) Outer flattened periderm ~5-6 wks Inner, cuboidal germinal (basal) layer The embryonic epidermis begins to proliferate (epidermal stratification) ~7 wks Fetal basement.M ~8 wks Completed by second trimester (5th m ) Tooth primordia- ‫برعم‬ Prof: Hamida Aldwibe-2024  First trimester The underlying layer of proliferating cells is now called the basal layer At 11th wk  the proliferation of basal layer  a new intermediate layer just deep to the peridem, & basal layer now called the germinative layer or stratum germinativum ( stem cells ) that will continue to renew the epidermis through life. ~5-6 wks at 11 wks The mesenchymal cells begin to produce at 11 wks collagenous & elastic c.t. fibers Fibroblasts appear 6 – 8th wks beneath the epidermis  Prof: Hamida Aldwibe-2024 : First trimester Primordial vasculature formed 9–12 wks- (Ali khan) ~8–12 wks 9 wks Appearance & migration into Distinct border between epidermis: epidermis and dermis Melanocytes (12wk) Langherhans.C (12wk) (DEJ present) Merkel cells (12wk) First trimester ~9–12 wks Appearance of: 1) Anchoring filaments/ fibrils 2) Hemidesmosomes (3 months) - Hair follicle & nail primordia (buds) seen - Vasculature formed Prof: Hamida Aldwibe-2024 Second trimester ~12 wks Formation of dermo-epidermal junction (DEJ) - Nail bed starts to keratinize - Proximal nail fold forms Type III collagen appears Prof: Hamida Aldwibe-2024  Second trimester ~12–14 wks Parallel ectodermal ridges (finger prints) Fibroblasts actively synthesizing collagen & elastin in dermis Eccrine & sebaceous Prof: Hamida Aldwibe-2024 gland primordia seen  Second trimester (12 - 20 wks) 12 wks Melanocytes present in epidermis 12–16 wks Melanin production 16–18 wks Initial fat formation in sub.cutis 16–20 wks Melanocytes proliferate and become fully functional to transfer melanosomes to keratinocytes Melanosome transfer 20 wks: Mature thickness of dermis & dermal ridges present Prof: Hamida Aldwibe-2024  Second trimester ~12–24 wks Hair follicles differentiate ~15–20 wks - Periderm is shed ~22 wks (periderm is part of -Trunk eccrine ~22–24 wks vernix caseosa) [20–21 wks] gland primordia - Mature epidermis complete -Follicular keratinization -Elastic fiber seen - Adipocytes appear under -Nail plate completely dermis covers nail bed -Papillary/reticular boundary distinct -Dermal ridges appear Prof: Hamida Aldwibe-2024 ~15–20 wks-----Periderm is shed -Periderm is a part of vernix caseosa)[20–21 wk] - A white, cheesy or waxy, biofilm which covers the skin of the fetus during the third trimester of pregnancy - Is a naturally occurring, complex, lipid-rich substance (proteolipid) produced by fetal sebaceous glands around 20th wk of geststion. - Is composed of water-containing corneocytes (80%), lipids (10%) and (10%) proteins.  Vernix caseosa  Performs several overlapping biological activities, including:  Protect skin of fetus from dehydration (Miniaturization)  Anti-infective  Antioxidant  Wound healing  Waterproofing.  Serves as a mechanical barrier & vaginal lubricant, & facilitating parturition  Layers *«Y of skin ers oI  Composed Composed of 33 layers: of layers  1) 1) Epidermis: Epidermis Hypocâermis  Is Is composed of cellular components composed ofcellulor components only only Deep fascia Muscle  2) Dermis: Hair shaft  Is formed of Is formed of33 types types of components: of components: Dermal papillae Epidermis  Cellular Cellulor Subpapillary vascular:! plexus layer  Fibrous Fibrous matrix motrix (ground substance) (ground substonce) Pore Appendages ofsklé  Collagen Collogen&& elastic fibers elostic fibers Amis Reticular Eccrine sweat gland) layer Arrector pili muscle  Also is Also the site is the site of vascular, lymphatic of vosculor, lymphotic&& Sebaceous (oil) glan“ Hair follicle nerve nerve network. network. Halr root 3) Subcutis Subcutis (Hypodermis): /t¥aperficiaI fascia)  3) (Hypodermis): 'Nervous structures  Contains Contoins adipose tissue, large odipose tissue, vessels & forge vessels& Sensory nerve fiber Lamellar (Pacinian) Dermal vascular plexus nerves nerves corpuscle Hair follicle receptor Prof: Prof: Hamida Aldwibe-2024 Hamida A/dwi6e-2024 Main types of human skin: Glabrous (non-hairy) skin Non Glabrous (Hairy) skin  Thick epidermis  Thin epidermis ()  Stratum lucidum.  Lacks st. lucidum  Presence of encapsulated sense  Absence of encapsulated SO. organs in the dermis  Lack of hair.F & sebaceous G  Has both hair.F & sebaceous. G  Has fewer sweat glands & sensory receptors.  Palms & soles (acral skin)  Rest of body  Presence of epidermal ridges  Absence of epidermal ridges (Dermatoglyphics) (Dermatoglyphics) Prof: Hamida Aldwibe-2024  Thick skin Thin skin (hairless) (hairy) Thin epidermis Thin Thick epidermis 44 layers foyers 55 layers foyers Less prominent st.C st. C Prominent st. C Less developed st.G st. G Well developed st.G st. G , „„„„„ f,„ t= Thicker. dermis Thicker. Thinner. dermis Most body surfoces surfaces Palms Polms&& soles -” ” ” ,$+‘ Hair. Hoir.FF&& seb.G seb. G No No HF HF&& seb.G seb. G sta1us Dasei Prof: Hamida A/dwi6e-2024 Aldwibe-2024  Skin vories varies in thickness among omong anatomic onotomic location, sex, & age locotion, sex,& oge of the individual. the individuol.  Skin is Skin thickest on is thickest the palms on the polms&& soles soles (1.5 (1.5 -- 1.6 1.6 mm) mm) The thinnest  The thinnest skin skin is found on is found the eyelids on the eyelids (0.04 (0.04 mm mm -- 0.1 0.1 mm). mm). Male skin is thicker thon  Mole than femole. female.  Children Children have hove relatively thin skin. relotively thin skin.  Thisvarying thickness represents vorying representsoa difference in dermal dermol thickness As epidermal  As epidermol thickness is rather rother constant constont throughout life. Prof: Prof: Hamida Aldwibe-2024 Hamida A/dwi6e-2024  Normal acral skin (palms & soles)  St. corneum is compact  Thicker epidermis > other sites of body  Presence of st. lucidum at base of S.C (Clear zone separating st.c. from st. G.)  Relatively fewer melanocytes in epidermis  Meissners corpuscles in papillary dermal tips  Increased dermal collagen with diminished space between bundles  No piloseb. Units  Many eccrine structures. Prof: Hamida Aldwibe-2024 Normal skin: Trunk.  St. corneum, st. granulosum, st. spinosum & st. basale.  Tightly packed dermal collagen is seen near the DEJ.  loosely arranged collagen is found deeper in the dermis.  A cluster of small blood vessels & nerves is seen in the dermis. Prof: Hamida Aldwibe-2024  Mucosa Parakeratosis  Is not skin  Parakeratosis is normal in it  No basket-weave orthokeratosis.  Lacks granular layer  Keratinocytes have abundant glycogen (appear very pale)  Plasma cells are a normal part of inlfam. Infiltrate in sub-mucosa  No piloseb. Units- (Fox fordyce spots).  Salivary. G. & ducts may be present. Prof: Hamida Aldwibe-2024  Epidermis (Epi) coming from Greek (over or upon) Outermost visible layer of called: Cuticle (scarf) Prof: Hamida Aldwibe-2024  Epidermis AA vosculor vascular Hair shaft Dermal papillae Dependent on the the Subpapillary vascular underlying underlying dermis dermis for Epidermis Papillary nutrient nutrient delivery plexus layer Pore delivery /rmis Eccrine sweat gland Waste disposal Appendages ofskin’ Woste via disposol vio diffusion through the Reticular layer Arrestor pili muscle ’ Sebaceous (oil) gland ! Hair follicle Hair root DEJ. , ypodermis superficial fascia) S Small Oll nerve nerve endings Nervous structures Sensory nerve fiber ** D ermalvascular plexus endings Lamellar (Pacinian) corpuscle , Adipose tissue Hair follicle receptor “ ' —(r.o.o.t afr,p%lex-uñ'l- Prof: Hamida A/dwi6e-2024 Aldwibe-2024 - Gives strength to the skin. Appendages - Forms the waterproof, protective warp over the body surface - Acting as semi-impermeable barrier. - Serves as a barrier to prevent fluid loss - The barrier that prevents most substances from entering the body from outside ( infection & chemicals) - Provides immunological protection Sebaceous gland - Synthesizes vit. D3 Prof: Hamida Aldwibe-2024  Epidermis Epidermis made mode up of: upof: @RttJM O0fflOtJM 55 distinct distinct keratinized kerotinized SPatum lucldum Stratified squomous Strotified squamous /ssaumganuDs‹xñ epithelium layers foyers Udng keralnocytw 44 main of cells moin types of cells ’ ”’ ’ Langerhans call t "°*"* Consisting mostly of of keratinocytes kerotinocytes Uakel call Prof: Hamida Afdwiöe-2024 Aldwibe-2024 5 Layers of epidermis 5†ra†uø granulosum Stratucsp st Stratuøba Structure of the skin  Basal layer along St. with St. spinosum Malpighian = Malpighian layer Prof: Hamida Aldwibe-2024  Epidermal cells Keratinocytes Melanocytes Neuro-ectoderm Ectodermal 90-95% 3-5%--10% Neural crest Neuro-ectoderm 3–5% Mesoderm Langerhans Merkel cells  Keratinocytes  Are the primary cells of the epidermis  Mainly responsible for the production of proteins ( keratin filaments) form cytoskeleton of the epidermal cells.  Provides resilience (‫)صمود‬, structural integrity, along with serving as a marker for differentiation (ie. K5/14 –basal. L)  To a lesser degree produce other proteins & sterols  Produce lipids important for barrier function Prof: Hamida Aldwibe-2024  Keratinocytes  May have an immunological function:  Can produce pro-inflammatory cytokines:  IL-1 (especially), IL-6, IL-8, IL-10, IL-12, and TNF-α  Express on their surface immune reactive molecules such as:  MHC class II antigens (e.g. HLA-DR) &  Intercellular adhesion molecules (ICAM-1)  Respond to IL-2, IL-4, IL-13, IL-22, and TNF-α Prof: Hamida Aldwibe-2024  CD207 CD207 (langerin; (longerin: most most sensitive sensitive IHC IHC stain; Appearance & Appeoronce& c«„»«» «»si - ED'em dri6i histiocytes histiocytes specific for Birbeck specific for Birbeck granules) gronules) stoin: migration migrotion into CD1a CD1o S100 S100 epidermis CD34 CD34 ~8–12 wks Actin and ond vimentin MiTF = Microphthalmia transcription factor (sensitive- specific) S100 HMB45 Pigment-producing - Cytokeratin Cytokerotin = CK20 or tonofilaments - S100 Contain Contoin CK8, CK8, 18, and 19 18,ond 19 LariqerMarisoeUariciJVIerVelceN.  Langerhans Cell (LC) Major antigen presenting cells (APC) On On EM, characteristic Originate from CD34+ progenitor progenitor cells in bone. M M folded reniform reniform (kidney (kidney Connected Connected&& Interact with k. lnteroct with via E-cadherin k. vio receptors E-codherin receptors shaped) nuclei shaped) nuclei Tennis racket-shaped Tennis rocket-shoped Found Found mainly moinly in st. spinosum, inst. spinosum, where where it first it first Birbeck Birbeck granules gronules encounters encounters and ond processes processes antigens ontigens Melanocyte Melonocyte ‘” ) Merkel cells Slow-adapting mechanoreceptors typeI type I Found Found in skin, hair, inskin, hoir, uveal tract of uveol troct of Found ininareas areas with high tactile sensitivity (lips, eye eye (choroid, iris, ciliary (choroid, iris, ciliory body), body), fingertips, ORS ORS of hair follicle, follicle, oral mucosa) leptomeninges, leptomeninges, and ond inner inner ear eor (striae vascularis of (strioe vosculoris of cochlea) cochleo)  Epidermal –melanin unit Melanocytes do not form junctions with keratinocytes Melanocytes resides in Melonocytes in basal bosol layer ratio of loyer with rotio ofJ1 melanocyte to 10 melonocyte to JO basal bosol keratinocytes kerotinocytes Each Eoch melanocyte interfaces with 36 melonocyte inteñoces 36 keratinocytes kerotinocytes when analyzed onolyzed three dimensionally dimensionolly (epidermal (epidermol melanin melonin unit)  Positive immunostains for LCs  CD207 (langerin; most sensitive IHC stain; specific for Birbeck granules)  CD1a  S100  CD34  Contains actin and vimentin (immunostains)  Exposure to UV radiation causes depletion of LCs and decreases ability to present antigen ( immune surveillance)  Merkel cells  EM shows  Microvilli at cell surface  Dense core granules  Lobulated nucleus, and  Intermediate filaments assuming whorled arrangement near nucleus (dot-like pattern)  Contain battery of neuropeptides and neurotransmitter-like substances:  Neuron-specific enolase (NSE)  Vasoactive intestinal peptide (VIP)  Calcitonin gene-related peptide (CGRP)  Chromogranin A / Synaptophysin, & Met-enkephalin Other Epidermal cells 1. Granstein cells 2. Indeterminate cells  Granstein cells Most recently skin’s immune cells discovered  Least understood  Interact with cells (suppressor T. ) that carry out immune response  Probably acting as a brake on the skin activated immune response  Suppressor signals that keep immune response under control  Less susceptible to damage by UVR > Langerhans.  Indeterminate cells Dendritic cells Morphologically resemble LG. Absent Birbeck granules. Positive Iα antigen (CD1a)  Epidermis  Dividedinto 5 main layers with characteristic:  Cell shape  Specialized intracellular structures  Types of keratin  Accessory cells  Proteins Prof: Hamida Aldwibe-2024 Basal layer/Stratum basale/ St. germinativum  Lower most layer  Single layer of:  Basophilic cuboidal (columnar) cells (K)  Large , dark-staining nuclei.  Most basophilic (Dark) dense cytoplasm in epidermis  Contain pigmented melanosomes Basal transferred from melanocytes by layer phagocytosis.  Mitotically active cells. Prof: Hamida Aldwibe-2024 Stratum. germinativum /basal layer/St. basale  Primary site for mitotically active cells (germinative layer)  Cell division 18-19 days  Proliferates continuously with repeated mitotic division  Not all basal cells have potential to divide  Gives rise to all other Keratinocytes of epidermal layer Prof: Hamida Aldwibe-2024  Stratum basale cells: - There are 3 main population cells: 1- 10% stem cells. (mitotically active) Stem cells give rise to TAC. 2- Transient amplifying cells Basal (TAC). layer 3- Post-mitotic cells. Prof: Hamida Aldwibe-2024  10% Regenerate themselves Divide & differentiate ‫هرمة‬  St. Germinativum (Basale)  The epidermis renews itself continuously by cell division (mitosis) in it’s deepest ( basal layer).  Renewal of the epidermis takes approximately 26 to 28 days:  13 to 14 days for maturation from basal layer to corneum &  Another 13 to 14 days for shedding Basal ( desquamation ) layer Dr: Hamida Aldwibe-2023 AoneAfter e a mitotic o c division on a newly ne y formed cells ce will undergo un e o a progressive maturation moturotion called colled keratinization kerotinizotion asos its 13 to toJ4 14 days doys migrates surface. migrotes to the surfoce. 13 toJ4 J3 to 14 days doys Stratum corneum Cornification/ dead/ Keratin StratumLucidum Only inthick epidermis.  Stratum basale cells: Langerhans cells (mainly in st. spinosum) Melanocytes (Supra basal) lying between basal cells in a ratio of 1: 10 Basal Keratinocyte Merklelayer cells (basal) Prof: Hamida Aldwibe-2024  ELECTRON MICROSCOPY (basal Layer) - Contains tono-filaments = Intermediate keratin filaments K5 / K14 (KIF) (K5/K14) expressed in it. expression Which inserted into both desmosomes & defective in hemidesmosomes & form EBS keratinocyte cytoskeleton -K19 found in basal cells at transitional boundaries between different types of epithelia  Desmosomes  Cells are bound to each other by major junctional adhesion structures called desosomes.  ( Intercellular adhesions = bridges).  = Anchoring junctions that connect adjacent k.  Ca++ dependent cell surface structure that promote adhesion  Attach to BM (basal lamina) via intermediate keratin filaments (K5/K14) by hemidesmoses. Prof: Hamida Aldwibe-2024  Basal cells contain: Ornithine decarboxylase ↑ ornithine decarboxylase expression (ODC) Is a marker for proliferative activity Keratinocyte Melanocyte Prof: Hamida Aldwibe-2024  Function of ornithine decarboxylase  The ornithine (a product of the urea cycle)  The ornithine decarboxylation reaction catalyzed by ODC is the first & committed step in the synthesis of polyamine.  Polyamines, particularly putrescine, spermidine & spermine.  Are compounds required for cell division  Are important for:  Stabilizing DNA structure  The DNA double strand-break repair pathway  As antioxidants.  Therefore, ODC is an essential enzyme for cell growth, producing the polyamines necessary to stabilize newly synthesized DNA. Prof: Hamida Aldwibe-2024 Ornithine decarboxylase expression (ODC) Stimulated by: Inhibited (Partially blocked) by:  Cellular proliferation stimulated  Retinoic acid by various factors, including:  Corticosteroid  Trauma  Vitamin D3  UV (UVB)  In psoriatic skin ( hyperproliferation of.K )  EGF  ( inhibeted by retinoids & steroids by  Androgens (Estrogens) blocking of induction of epidermal  β agonists ornithine decarboxylase activity )  Tumor promoters (chemicals,  Eflornithine = difluoro - methylornithine cytokines) ( Effectively reduce cancers in animal  Asbestos (miners) models) Prof: Hamida Aldwibe-2024