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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