Histology of Skin. dr. Alya Amila Fitrie, M.Kes dr. Radita Nur Anggraeni Department of Histology Medical Faculty University of North Sumatera 2008

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1 Histology of Skin dr. Alya Amila Fitrie, M.Kes dr. Radita Nur Anggraeni Department of Histology Medical Faculty University of North Sumatera

2 INTRODUCTION The heaviest single organ of the body, 16% of TBW. Presenting 1,2 2,3 m 2 of surface. Composed of : Epidermis : an epithelial layer of ectodermal origin Dermis : a layer of connective tissue of mesodermal origin. 2

3 Comparative thickness of the skin 3

4 EPIDERMIS Consist mainly of a stratified squamous keratinized epithelium keratinocytes. Three << abundant cell types : 1. Melanocytes : neural crest-derived cell 2. Langerhans cell : derived from bone marrow precursor 3. Merkel s cell : neural crest-derived cell 4

5 Five layers of keratin-producing cells (keratinocytes) : 1. Stratum basale (t (stratum t germinativum) 2. Stratum spinosum 3. Stratum granulosum 4. Stratum lucidum 5. Stratum corneum 5

6 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 t renewal of epidermal cells. Human epidermis is renewed about every days. 6

7 Stratum spinosum Consists of cuboidal or slighly flattened cell, a central nucleus, a cytoplasm s processes : bundles of keratin filaments, a spine-studded st appearance ance (tonofilaments). The filaments : Maintaining cohesion among cells Resisting the effect of abrasion Stratum t basale + stratum t spinosum = stratum Malpighi mitoses 7

8 Stratum spinosum (cont.) Stratum spinosum of the thick skin from sole of the foot. Pararosaniline-toluidine blue. Medium magnification 8

9 Stratum granulosum Consists of 3-5 layers of flattened polygonal l cells, cytoplasm filled with keratohyalin granules. The membrane-coated lamellar granules : containing i lamellar ll 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 9

10 Stratum lusidum Translucent, thin layer of flattened eosinophilic epidermal cells. Organelles & nuclei (-) Cytoplasm : densely packed keratin filaments Desmosom (+) between adjacent cells 10

11 Stratum corneum Cornified envelope lipids Consists of layers of fflattened nonnucleated 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 11

12 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 (-) 12

13 Melanogenesis php?pos=bl&im=images/melanocyte%20develop ment%20and%20pigmentation.jpg 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. 13

14 Melanocyte Melanin granules accumulate in the supranuclear region of the cytoplasm protecting from deleterious effects of solar radiation. 14

15 Langerhans Cells Star-shaped Location : stratum spinosum Bone marrow-derived Important in immunologic skin reaction 15

16 Merkel s Cells Generally in the thick skin of palms and soles. Resemble the epidermal epithelial l cells, with small dense granules in cytoplasm. Free nerve ending at the base. 16

17 Immunologic Activity in the Skin Its large size Lymphocytes >>> Antigen-presenting g cells (APC) Close contacts with antigenic molecules Epidermis has an important role in some types of immune response 17

18 DERMIS Dermis is connective tissue that Support epidermis i Binds epidermis to hypodermis The thickness : varies The surface : irregular dermal papillae >< epidermal ridges. Contains 2 layers : Papillary layer Reticular layer 18

19 Papillary Layer Composed of : Loose connective tissue Fibroblasts Other connective tissue cells : mast cells & macrophages Extravasated leukocytes Anchoring fibrils (+) : special collagen fibrils 19

20 Reticular Layer Composed of : Irregular dense connective tissue (type I collagen) More fb 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 20

21 DERMIS (cont ) Rich network of blood & lymph vessels. Arteriovenous shunt temperature regulation. In addition, dermis contains : epidermal derivatives : Hair follicle Sweat & sebaceous glands Nerves 21

22 Subcutaneous Tissue Consists of loose connective tissue. Contain fat cells that vary in number & size. Referred to superficial fascia, >> panniculus adiposus 22

23 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. 23

24 Skin Sensorial Receptors Free nerve endings The expanded : Ruffini endings The encapsulated : Vater-Pacini Meissner Krause. 24

25 Meissner & Paccinian corpuscle 25

26 GLANDS OF THE SKIN Sweat glands Sebaceous glands Eccrine Apocrine Mammary gland 26

27 Sweat Gland Ecrine (merocrine) sweat gland Simple coiled tubular gland Throughout skin important in regulation of body temperature 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 27

28 Sweat Gland 28

29 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 infections (e.g. with the development of acne) 29

30 Sebaceous Gland 30

31 HAIRS Elongated keratinized structure Develop from epidermis & invade the dermis & hypodermis Everywhere except palms, sole, glans penis, clitoris & labia minora Hairs grow discontinously have periods of growth (anagen) followed by period of rest (telogen) In scalp : growth period several years, rest period 3 months Hair in scalp, face & pubis strongly influenced by androgens, adrenal & thyroid hormones 31

32 Hair follicle 32

33 NAILS Highly keratinized epithelial cells arranged in plates of hard keratin Develop from nail matrix nail root Stratum corneum forms eponychium or cuticle nail plate Nail plate on nail bed 33

34 Histology of Nail E=eponychium, H= hyponychium, N=nail plate, DP=distal phalanx 34

35 References Junqueira, L.C. & Carneiro, J. Basic Histology, Text & Atlas, 11 th edition, Lange Medical Books McGraw-Hill Gartner, L.P. & Hiatt, J.L. Colour Textbook of Histology, Third Edition Kierszenbaum AL. Histology & Cell Biology, An Introduction to Pathology, 2 nd ed. Mosby Elsevier

36 Terima kasih. 36