Integumentary System

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Integumentary System
By
Jittipan Chavadej , Ph.D.
Anatomy Dept.,Fac. of Science
yr.,2000
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• 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 layersupl layer
  of peridermal cells

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Diagram showing the formation of the skin at
various stages of development
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• 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

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Melanoblast (-cyte) -derived from neural
crest -midpregnancy-begin producing pigment
granules melanosomes

• Dark skin-more pigment granules/cell

Albinism -genetic trait, lack of
enzyme-tyrosinasetyrosine melanin
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Epidermal differentiation
Movement of epidermal cells - loss of
adhesiveness e.g. fibronectin, laminincollagen
types IIV
Keratohyalin granules (histidinesulphur- rich),
(closely associated with keratin filament)-
stratum granulosum (keratinocyte)
Keratin filaments-stratum corneum
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• 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
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One of the prominent features of thick
skinpresence of epidermal ridges and creases
-gtloops whorls
Dermatoglyphics-basic patterns(epi. ridge) for
genetic analysis or criminal investigation
(unique to individual)
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Dermis

• Mesodermal cells from dermatome / beneath
  ectoderm

• 3rd month -transition from highly cellular
  embryonic form fibroblast fibrous intercellular
  matrix

• Becomes highly vascularized sensory nerve

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Future dermis-loosely aggregated mesenchymal
cells
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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
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Diagram showing development of a hair and a
sebaceous gland
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• 5th mo. hair shaft-keratinization forming
  granules of trichohyalin(hardness of the hair)

• Late stage of hair formation-hair bulb--gt
  melanocytes --gtcolor

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Mammary Gland

• Mammary line or ridge(6 wk.) base of forearm
  region of hind limb

Small solid outbudding lactiferous duct
formationalveoli of the gland epithelial pit
(nipple-after birth)
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Diagram showing position of mammary line
Stages in the embryonic development of the human
mammary gland
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Abnormalities of Skin Development

• Ichthyosis-genetically transmitted disorders of
  keratinization

• Harlequin -autosomal recessive disorder

• Hypertrichosis- formation of hair follicle

• Atrichia -congenital absence of hair

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Amilk line-mammary glands form along this
line Bcommon sites of formation of supernumerary
nipples/mammary gland
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• Polythelia - accessory nipples(axillary region)

• Polymastia -supernumerary brests