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Histology (Skin) - Part 1
 

Histology (Skin) - Part 1

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    Histology (Skin) - Part 1 Histology (Skin) - Part 1 Presentation Transcript

    • THE SKIN By P.D.Sanaa El-Sherbiny Mansoura University
    • Function of theskinand protects the body. Covers Control internal temperature. Produces vitamin D. Receptors to detect environmental stimuli. Regulates the movement of substances into and out of the body Forms the largest organ of the body forms 16%of body weight Bio 130 Human Biology
    • Skin structure Epidermis: is outermost layer. Stratified squamous keratinized epithelium.  Keratinization production of a waterproof protein.  Pigments. Dermis: living portion of skin mostly dense connective tissue.  Contains :C.T fibers &cells ,vessels, sweat glands, sebaceous glands, hairs. Hypodermis :Adipose tissue Contains receptors Bio 130 Human Biology
    • Types:1-THICK SKIN EPIDERMIS IS THICK:0.8mm in palm ,1.4 mm in sole. Contains 4 types of cells: 1-keratinocytes (85% of cells) 2-Melanocytes 3-Langerhans cells 4-Merkel cells ِArranged in five layers.
    • 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
    • Layers of epidermis are  Stratum basale (germinativum)  Stratum spinosum  Stratum granulosum  Stratum lucidum (may not be present)  Stratum corneum
    • Layers of epidermis  Stratum basale (germinativum)  Single layer of cells on basal lamina  Stem cells which give rise to keratinocytes  Contain melanin transferred from melanocytes  May see mitotic figures  Desmosomes and hemidesmomes
    • Layers of epidermis  Stratum spinosum  Several cells thick  Have cytoplasmic processes (spines)  Desmosomes
    • Layers of epidermis  Stratum granulosum  1 to 3 layers of fusiform shaped basophilic cells  Keratohyalin granules contain cystine-rich and histidine-rich proteins that associate with keratin filaments
    • Layers of epidermis  Stratum lucidum  Present only in thick skin  Cells in which keratinization is advanced
    • 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 in thickness
    • TYPES OF EPIDERMAL CELLS
    • The epidermal cells:1-keratinocytes  They are responsible  For keratin formation  Formed of many layers that continuously shed  And regenerate every 2-4 weeks  They are arranged  In many layers.
    • :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 protein synthesizes (rER, Golgi, mitochondria &melanosomes). They form melanin by tyrosinase from tyrosine amino acid By converting it to dioxyphenyl alanine DOPA
    • :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
    • Langerhans cells
    • Merkels cells-4 Found in basal cell layer Are modified epidermal cells Sensory nerve fibers form terminal disk under Merkels cells Function as touch receptors
    • THIN SKIN ALLOVER THE BODY EXCEPT SOLE & PALMS. EPIDERMIS ISTHINNER,ST.spinosum,2-4LAYERS,ST.GRA. ONE INCOMPLETE LAYER:NO ST LUCI. ,ST,COR.THINNERNUMEROUS SWEAT GLANDS.*CONTAIN HAIRE, SEBACEOUS GLANDS*AND ERECTOR PILLI MUSCLE
    • THIN SKIN
    • 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
    • Meissner‘s )Tactile( Corpuscle Located in the dermlpapillae Receptor for light touch 28
    • Reticular layer -2 The thicker deep layer Formed of dense c.T rich in interlacing wavy collage fibers It is less cellular &less vascular Contain many nerve receptors: Krause end bulbs Ruffini corpuscles Pacinian corpuscles
    • :Glands and skin appendages Sebaceous glands  Clumps of epithelial tissue distributed within dermis  Secrete “sebum”—oily, fat-based substance that is also anti-bacterial  Located all over body Sweat glands  Microscopic clumps of epithelial tissue distributed within dermis, duct extends out through dermis to pore their secretion.  More than 2.5 million glands per person  Eccrine sweat glands, concentrated on hands and soles of feet and forehead, secrete sweat to cool body, also at conditions of fear and emotion.  Apocrine glands, concentrated in armpits and groin, analogous with sexual scent glands of other animals, odor comes from bacteria that concentrate here.  Ceruminous glands: modified sweat glands in ear canal produce ear wax
    • 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
    • SWEAT GLANDS Merocrine glands:  Apocrine glands: Allover the body  Axilla,groin,pubic Secretory cells 2types region Clear cells cubical rich in  Secretory part similar glycogen granules.  To mero. With wider Dark with narrow basal part 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 follicles cubical cells  Secretion stim.by sex  hormons