Histology of Skin
dr. Alya Amila Fitrie, M.Kesd R dit N A idr. Radita Nur AnggraeniDepartment of Histology
Medical Faculty University of North Sumatera2008
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2008
INTRODUCTION
• The heaviest single• The heaviest single organ of the body, 16% of TBW16% of TBW.
• Presenting 1,2 – 2,3 m2 of surface.d f• Composed of :
– Epidermis : an epithelial layer of ectodermal originectodermal origin
– Dermis : a layer of connective tissue of mesodermal origin
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mesodermal origin.
Comparative thickness of the skin
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EPIDERMIS
C i t i l f• Consist mainly of a stratified squamous keratinized epithelium → keratinocytes.→ keratinocytes.
• Three << abundant cell types :1 Melanocytes : neural crest-derived cell1. Melanocytes : neural crest-derived cell2. Langerhans cell : derived from bone marrow
precursor
43. Merkel’s cell : neural crest-derived cell
Five layers of keratin-producing cells (keratinocytes) :
1. Stratum basale ( t t i ti )(stratum germinativum)
2. Stratum spinosum3 Stratum granulosum3. Stratum granulosum4. Stratum lucidum5. Stratum corneum
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Stratum basaleStratum basale (Stratum germinativum)• Single layer of basophilic columnar or cuboidal
cell resting on basement membrane at the dermal-epidermal junction.
• Desmosom (+), hemidesmosom (+)• Stem cells → intense mitotic activity & is
responsible, in conjunction with the initial ti f th t l f t t l fportion of the next layer, for constant renewal of
epidermal cells.• Human epidermis is renewed about every 15 30
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• Human epidermis is renewed about every 15-30 days.
Stratum spinosump• Consists of cuboidal or slighly
flattened cell a central nucleusflattened cell, a central nucleus, a cytoplasm’s processes : bundles of keratin filaments, a spine st dded appea ancespine-studded appearance (tonofilaments).
• The filaments : a– Maintaining cohesion among cells– Resisting the effect of abrasion
St t b l t t• Stratum basale + stratum spinosum = stratum Malpighi → mitoses
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Stratum spinosum (cont.)
Stratum spinosum of the thick skin from sole of the
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pfoot. Pararosaniline-toluidine blue. Medium magnification
Stratum granulosumg• Consists of 3-5 layers of
fl tt d l l llflattened polygonal cells, cytoplasm filled with keratohyalin granules.
• The membrane-coated lamellar granules : i i l ll di k h f d bcontaining lamellar disks that are formed by
lipid bilayers. This granules : fuse with cell membrane → discharge their contents →membrane → discharge their contents → intercellular spaces of stratum granulosum → form of sheets containing lipid
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g p
Stratum lusidum
• Translucent, thin layerTranslucent, thin layer of flattened eosinophilic epidermal cellsepidermal cells.
• Organelles & nuclei (-)• Cytoplasm : densely packed keratin
filaments• Desmosom (+) between adjacent cells
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Stratum corneum Cornified envelope lipids
• Consists of 15-20 layers f fl tt d lof flattened nonnuclea-
ted keratinized cells.• Cytoplasm :
a birerfringent filamentous scleroprotein, keratin.
• After keratinization, the cells consist of only fibrillar & amorphous proteins; & thickened plasma membrane → horny cells or corneocyte
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Melanocytesy
• A specialized cell of the epidermis found b th b t th ll f thbeneath or between the cells of the stratum basale & in the hair follicles.
• Derived from neural crest cells.
•Hemidesmosomes(+)•Hemidesmosomes(+), desmosome (-)
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Melanogenesisg
http://www.ambion.com/tools/pathway/loadImage.php?pos=bl&im=images/Melanocyte%20Development%20and%20Pigmentation.jpg
• Tyrosinase is synthesized in the RER, accumulated in GoC → vesikel : melanosom. Melanin synthesis in the melanosom II → melanosom III → melanin granules. M l i l i t & t f d t th k ti t f th
ment%20and%20Pigmentation.jpg
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• Melanin granules migrates & transferred to the keratinocytes of the malpighian layer.
Melanocyte
• Melanin granules accumulate in the supranuclear region p gof the cytoplasm → protecting fromprotecting from deleterious effects of solar radiation.
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Langerhans Cells
• Star-shaped• Location : stratumLocation : stratum
spinosum• Bone marrow derived• Bone marrow-derived• Important in immunologic skin
ireaction
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Merkel’s Cells
• Generally in the thick skin of palms and solesskin of palms and soles.
• Resemble the epidermalith li l ll ithepithelial cells, with
small dense granules in cytoplasm.• Free nerve ending at the base.
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Immunologic Activity in the Skin
• Its large size• Lymphocytes >>>• Antigen-presenting cells (APC)g p g ( )• Close contacts with antigenic molecules
Epidermis has an important role in some types of immune response
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DERMIS• Dermis is connective tissue that
S t id i– Support epidermis– Binds epidermis to hypodermisTh thi k i• The thickness : varies
• The surface : irregular→ dermal ill >< id l idpapillae >< epidermal ridges.
• Contains 2 layers :– Papillary layer– Reticular layer
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Papillary Layer
• Composed of :– Loose connective tissue– Fibroblasts– Other connective tissue cells : mast cells &
macrophages– Extravasated leukocytes
• Anchoring fibrils (+) : special collagen fibrils
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Reticular Layer
• Composed of : – Irregular dense connective tissue (type I
collagen)f b f ll– More fibers, fewer cells.
• Contains a network of fibers of elastic system → responsible for the elasticity of the skin.
Thick section of skin stained for the fibers of
the elastic fibers.
Weigert’s stain
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Weigert s stain
DERMIS (cont…)
• Rich network of blood & lymph vessels.• Arteriovenous shunt → temperature
regulation.• In addition, dermis contains : epidermal
derivatives :– Hair follicle– Sweat & sebaceous glandsSweat & sebaceous glands– Nerves
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Subcutaneous Tissue
C i t f l ti ti• Consists of loose connective tissue.• Contain fat cells that vary in number &
size.• Referred to superficial fascia , >> p ,
panniculus adiposus
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Skin & Lymphatic Vessels
• The arterial vessels → 2 plexuses :b t ill ti l l– between papillary – reticular layer
– between dermis – subcutaneous tissueTh 3 l• The venous → 3 plexuses :– Like arterial vessels + in the middle of the
dermisdermis.• Lymphatic vessels : begin as closed
sacs in the papillae of dermis → formsacs in the papillae of dermis → form two plexuses.
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Skin Sensorial Receptorsp
• Free nerve endings• Free nerve endings• The expanded :
– Ruffini endings
• The encapsulated : – Vater-Pacini– Meissner– Krause.
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Meissner & Paccinian corpuscle
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GLANDS OF THE SKIN
• Sweat glands• Sebaceous glands
– Eccrine– Apocrine
• Mammary glandMammary gland
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Sweat Gland
– Ecrine (merocrine) sweat gland• Simple coiled tubular glandSimple coiled tubular gland• Throughout skin important in regulation of body
temperature• Secretory unit dark cells & clear cells• Secretory unit dark cells & clear cells
– Apocrine sweat gland• Found only in axilla, areola nipple, anal region • Modified apocrine sweat glands ceruminous glands of
ear, glands of moll in eyelids• Larger than eccrine, lumen of secretory tubulus is larger
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Sweat Gland
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Sebaceous Gland
• Secrete sebum oily substance• Empty secretory product into the upper
parts of the hair follicles Not found in palms of hand, soles of feet, sides of feet inferior of hairline
• Clinically the sebaceous glands are important in that they are liable to p yinfections (e.g. with the development of acne))
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Sebaceous Gland
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HAIRS• Elongated keratinized structure • Develop from epidermis & invade
th d i & h d ithe dermis & hypodermis • Everywhere except palms, sole,
glans penis, clitoris & labia minora• Hairs grow discontinously have
periods of growth (anagen) followed by period of rest (t l )(telogen)
• In scalp : growth period several years, rest period 3 months
• Hair in scalp, face & pubis strongly influenced by androgens, adrenal & thyroid hormones
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Hair follicle
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NAILS
• Highly keratinized epithelial cells arrangedepithelial cells arranged in plates of hard keratin
• Develop from nail matrix nail root
• Stratum corneum forms• Stratum corneum forms eponychium or cuticle
nail plate• Nail plate on nail bed
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Histology of Nail
• E=eponychium, H= hyponychium, N=nail plate, DP=distal phalanx
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References
• Junqueira, L.C. & Carneiro, J. Basic Histology, Text & Atlas 11th edition Lange Medical Books McGraw-HillAtlas, 11 edition, Lange Medical Books McGraw Hill. 2005
• Gartner, L.P. & Hiatt, J.L. Colour Textbook of Histology, Third Edition. 2007
• Kierszenbaum AL. Histology & Cell Biology, An Introduction to Pathology 2nd ed Mosby ElsevierIntroduction to Pathology, 2 ed. Mosby Elsevier. 2007
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Terima kasih….
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