histology (skin) - part 1

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  • 1.THE SKIN By P.D.Sanaa El-Sherbiny Mansoura University

2. Function of theskinand protects the body. Covers Control internal temperature. Produces vitamin D. Receptors to detect environmental stimuli. Regulates the movement of substancesinto and out of the bodyForms the largest organ of the bodyforms 16%of body weight Bio 130 Human Biology 3. Skin structure Epidermis: is outermost layer. Stratified squamous keratinized epithelium. Keratinization production of a waterproof protein. Pigments. Dermis: living portion of skin mostly denseconnective tissue. Contains :C.T fibers &cells ,vessels, sweat glands,sebaceous glands,hairs. Hypodermis :Adipose tissueContains receptorsBio 130 Human Biology 4. Types:1-THICK SKIN EPIDERMIS IS THICK:0.8mm in palm ,1.4mm in sole. Contains 4 types of cells: 1-keratinocytes (85% of cells) 2-Melanocytes 3-Langerhans cells 4-Merkel cells Arranged in five layers. 5. Epidermis anddermis Epidermis (purple) Dermal papillae Dermis Superficial papillary layer contains loose connective tissue, blood vessels, nerves, and lymphatics Deeper reticular layer has dense fibrous irregularly arranged connective tissue 6. Layers of epidermis are Stratum basale (germinativum) Stratum spinosum Stratum granulosum Stratum lucidum (may not be present) Stratum corneum 7. Layers of epidermis Stratum basale (germinativum) Single layer of cells on basallamina Stem cells which give rise tokeratinocytes Contain melanin transferredfrom melanocytes May see mitotic figures Desmosomes andhemidesmomes 8. Layers of epidermis Stratum spinosum Several cells thick Have cytoplasmic processes (spines) Desmosomes 9. Layers of epidermis Stratumgranulosum 1 to 3 layers of fusiform shaped basophilic cells Keratohyalin granules contain cystine-rich and histidine-rich proteins that associate with keratin filaments 10. Layers of epidermis Stratum lucidum Present only in thick skin Cells in which keratinization is advanced 11. Layers of epidermis Stratum corneum Superifical keratinized layer Cells Almost filled with keratin Flattened, non nucleate Coated with extra-cellular lipids that form water barrier of skin Layer that varies most inthickness 12. TYPES OF EPIDERMAL CELLS 13. The epidermal cells:1-keratinocytesThey are responsible For keratin formation Formed of many layers that continuously shed And regenerate every 2-4 weeks They are arranged In many layers. 14. :Melanocytes Found inbetween cells of the basal layer & At the basal part of the hair follicles. Branched cells with centeral nuclei By EM contains organells for proteinsynthesizes (rER, Golgi, mitochondria&melanosomes). They form melanin by tyrosinase fromtyrosine amino acid By converting it to dioxyphenyl alanineDOPA 15. :Langerhans cells -3 Found in upper layers of st.spinosum Have branched shape &central nuclei Represent 3-8%of epid. Cells Mesodermal in origin. EM not connected to keratinocytes &contain Birbeck granules Stained with silver & vital stains Phagocytic & antigen presenting cells 16. Langerhans cells 17. Merkels cells-4 Found in basal cell layer Are modified epidermal cells Sensory nerve fibersformterminal disk under Merkels cells Function astouch receptors 18. THIN SKIN ALLOVER THE BODY EXCEPT SOLE & PALMS. EPIDERMISISTHINNER,ST.spinosum,2-4LAYERS,ST.GRA.ONE INCOMPLETE LAYER:NO ST LUCI. ,ST,COR.THINNERNUMEROUS SWEATGLANDS.*CONTAIN HAIRE,SEBACEOUSGLANDS*AND ERECTOR PILLI MUSCLE 19. THIN SKIN 20. The dermis 1-Papillary layer : Forms dermal papillae Loose C.T rich in collagen type 111 Elastic fibers,C.T cells and rich in blood capillaries Contain meisssners corpuscles 21. Meissners )Tactile( Corpuscle Located in the dermlpapillae Receptor for light touch 28 22. Reticular layer -2 The thicker deep layer Formed of dense c.T rich in interlacing wavycollage fibers It is less cellular &less vascular Contain many nerve receptors: Krause end bulbs Ruffini corpuscles Pacinian corpuscles 23. :Glands and skin appendages Sebaceous glands Clumps of epithelial tissue distributed within dermis Secrete sebumoily, fat-based substance that isalso anti-bacterial Located all over body Sweat glands Microscopic clumps of epithelial tissue distributedwithin dermis, duct extends out through dermis topore their secretion. More than 2.5 million glands per person Eccrine sweat glands, concentrated on hands andsoles of feet and forehead, secrete sweat to coolbody, also at conditions of fear and emotion. Apocrine glands, concentrated in armpits and groin,analogous with sexual scent glands of otheranimals, odor comes from bacteria that concentratehere. Ceruminous glands: modified sweat glands in earcanal produce ear wax 24. sweat glands Two types of sweat glands Eccrine Not associated with hair follicle Duct segment less coiled, leads to epidermis Stratified cuboidal epithelium Secretory segment in deep dermis or hypodermis Secretory cells Myoepithelial cells lie between secretory cells, contraction expels sweat Apocrine Found in limited areas Empty into hair follicle 25. SWEAT GLANDS Merocrine glands: Apocrine glands: Allover the body Axilla,groin,pubic Secretory cells 2typesregion Clear cells cubical rich in Secretory part similarglycogen granules. To mero. With wider Dark with narrow basalpart with apical Lumen Glycoprotein granules Their ducts are lined Myoepithelialt cells With 2 layers of cubical cells Ducts lined by 2layers of but open into hair folliclescubical cells Secretion stim.by sex hormons