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Histology of Skin

dr. Alya Amila Fitrie, M.Kesdr. Radita Nur AnggraeniDepartment of Histology

Medical Faculty University of North Sumatera2008

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INTRODUCTION

• The heaviest single organ of the body, 16% of TBW.

• Presenting 1,2 – 2,3 m2 of surface.

• Composed of :– Epidermis : an epithelial layer

of ectodermal origin– Dermis : a layer of connective

tissue of mesodermal origin.

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Comparative thickness of the skin

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EPIDERMIS

• Consist mainly of a stratified squamous keratinized epithelium → keratinocytes.

• Three << abundant cell types :1. Melanocytes : neural crest-derived cell2. Langerhans cell : derived from bone

marrow precursor3. Merkel’s cell : neural crest-derived cell

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Five layers of keratin-producing cells (keratinocytes) :

1. Stratum basale (stratum germinativum)

2. Stratum spinosum3. Stratum granulosum4. Stratum lucidum5. Stratum corneum

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Stratum 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 portion of the next layer, for constant renewal of epidermal cells.

• Human epidermis is renewed about every 15-30 days.

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Stratum spinosum• Consists of cuboidal or

slighly flattened cell, a central nucleus, a cytoplasm’s processes : bundles of keratin filaments, a spine-studded appearance (tonofilaments).

• The filaments : – Maintaining cohesion among

cells– Resisting the effect of abrasion

• Stratum basale + stratum spinosum = stratum Malpighi → mitoses

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Stratum spinosum (cont.)

Stratum spinosum of the thick skin from sole of the foot. Pararosaniline-toluidine blue. Medium magnification

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Stratum granulosum

• Consists of 3-5 layers of flattened polygonal cells,

cytoplasm filled with keratohyalin granules.

• The membrane-coated lamellar granules : containing lamellar disks that are formed by lipid bilayers. This granules : fuse with cell membrane → discharge their contents → intercellular spaces of stratum granulosum → form of sheets containing lipid

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Stratum lusidum

• Translucent, thin layer of flattened eosinophilic epidermal cells.

• Organelles & nuclei (-)• Cytoplasm : densely packed

keratin filaments• Desmosom (+) between adjacent

cells

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Stratum corneum

• Consists of 15-20 layers of 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

Cornified envelope lipids

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Melanocytes

• A specialized cell of the epidermis found beneath or between the cells of the stratum basale & in the hair follicles.

• Derived from neural crest cells. •Hemidesmosomes(+),

desmosome (-)

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Melanogenesis

• Tyrosinase is synthesized in the RER, accumulated in GoC → vesikel : melanosom. Melanin synthesis in the melanosom II → melanosom III → melanin granules.

• Melanin granules migrates & transferred to the keratinocytes of the malpighian layer.

http://www.ambion.com/tools/pathway/loadImage.php?pos=bl&im=images/Melanocyte%20Development%20and%20Pigmentation.jpg

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Melanocyte

• Melanin granules accumulate in the supranuclear region of the cytoplasm →

protecting from

deleterious effects

of solar radiation.

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Langerhans Cells

• Star-shaped• Location : stratum

spinosum• Bone marrow-derived• Important in immunologic skin

reaction

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Merkel’s Cells

• Generally in the thick skin of palms and soles.

• Resemble the epidermalepithelial 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)• 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

– Support epidermis– Binds epidermis to hypodermis

• The thickness : varies• The surface : irregular→ dermal

papillae >< 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)– 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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DERMIS (cont…)

• Rich network of blood & lymph vessels.

• Arteriovenous shunt → temperature regulation.

• In addition, dermis contains : epidermal derivatives :– Hair follicle– Sweat & sebaceous glands– Nerves

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Subcutaneous Tissue

• Consists of loose connective tissue.• Contain fat cells that vary in

number & size.• Referred to superficial fascia , >>

panniculus adiposus

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Skin & Lymphatic Vessels

• The arterial vessels → 2 plexuses :– between papillary – reticular layer– between dermis – subcutaneous tissue

• The venous → 3 plexuses :– Like arterial vessels + in the middle of the

dermis.

• Lymphatic vessels : begin as closed sacs in the papillae of dermis → form two plexuses.

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Skin Sensorial Receptors

• Free nerve endings • The expanded :

– Ruffini endings

• The encapsulated : – Vater-Pacini– Meissner– Krause.

Meissner & Paccinian corpuscle

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GLANDS OF THE SKIN

• Sweat glands- Eccrine- Apocrine

• Sebaceous glands• Mammary gland

Sweat Gland

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Sweat Gland

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Sebaceous Gland

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Sebaceous Gland

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HAIRS

Hair follicle

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NAILS

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-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 Elsevier. 2007

• Pakurar AS, Bigbee JW. Digital Histology, an interactive CD atlas with review text, Wiley-Liss, 2004

• Berman I, Color Atlas of Basic Histology, Second Edition, Lange, 1998.

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Terima kasih….

Terima kasih…