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Integumentary System

Integumentary System. By. Jittipan Chavadej , Ph.D. Anatomy Dept.,Fac. of Science. yr. , 2000. Structural development begin as a single layer of ectodermal cells formation of a thin outer layer periderm at the end of the first month third month- three layers

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Integumentary System

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  1. Integumentary System By Jittipan Chavadej , Ph.D. Anatomy Dept.,Fac. of Science yr.,2000

  2. Structural development • begin as a single layer of ectodermal cells • formation of a thin outer layer periderm at the end of the first month • third month- three layers • - basal layer, intermediate layer&supl layer of peridermal cells

  3. Diagram showing the formation of the skin at various stages of development

  4. 6th month -epidermis beneath periderm differentiation into the definitive layers • Sloughs of peridermal cells into the amniotic fluid • Immigrant cells in the epidermis • -2nd month -melanoblast • -late in 1st trimester -Langerhans • cells • -Merkel cells

  5. Melanoblast (-cyte) : -derived from neural crest -midpregnancy-begin producing pigment granules = melanosomes • Dark skin-more pigment granules/cell Albinism -genetic trait, lack of enzyme-tyrosinase:tyrosine melanin

  6. Epidermal differentiation Movement of epidermal cells - loss of adhesiveness e.g. fibronectin, laminin&collagen types I&IV Keratohyalin granules (histidine&sulphur- rich),(closely associated with keratin filament)- stratum granulosum (keratinocyte) Keratin filaments-stratum corneum

  7. Lost nuclei -bag of densely packed with keratin filaments • 15-20 layers of dead cells Flattened cell-breaking up nuclear membrane Produce keratin filament (desmosome) Unspecialized cells - mitotic activity

  8. One of the prominent features of thick skin=presence of epidermal ridges and creases ->loops & whorls Dermatoglyphics-basic patterns(epi. ridge) for genetic analysis or criminal investigation (unique to individual)

  9. Dermis • Mesodermal cells from dermatome / beneath ectoderm • 3rd month -transition from highly cellular embryonic form fibroblast + fibrous intercellular matrix • Becomes highly vascularized + sensory nerve

  10. Future dermis-loosely aggregated mesenchymal cells

  11. Epidermal appendages Hair -induction from dermis -12th week :down growth of hair bud -hair papillae hair shaft epithelial hair sheath -arrector pili muscle :dermal root sheath & dermal papilla -sebaceous gl. fat-like substance hair follicle

  12. Diagram showingdevelopment of a hair and a sebaceous gland

  13. 5th mo. hair shaft-keratinization forming granules of trichohyalin(hardness of the hair) • Late stage of hair formation-hair bulb--> melanocytes -->color

  14. Mammary Gland • Mammary line or ridge(6 wk.) :base of forearm region of hind limb Small solid outbudding lactiferous duct formation+alveoli of the gland epithelial pit (nipple-after birth)

  15. Diagram showing position of mammary line Stages in the embryonic development of the human mammary gland

  16. Abnormalities of Skin Development • Ichthyosis-genetically transmitted disorders of keratinization • Harlequin -autosomal recessive disorder • Hypertrichosis- formation of hair follicle • Atrichia -congenital absence of hair

  17. A:milk line-mammary glands form along this line B:common sites of formation of supernumerary nipples/mammary gland

  18. Polythelia - accessory nipples(axillary region) • Polymastia -supernumerary brests

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