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Title:

Integumentary System

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begin as a single layer of ectodermal cells. formation of a thin outer layer periderm at ... Mammary line or ridge(6 wk.) :base of forearm region of hind limb ... – PowerPoint PPT presentation

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Title: Integumentary System


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 layersupl 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-tyrosinasetyrosine melanin
6
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
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
skinpresence of epidermal ridges and creases
-gtloops 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 showing development 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--gt
    melanocytes --gtcolor

14
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)
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
Amilk line-mammary glands form along this
line Bcommon sites of formation of supernumerary
nipples/mammary gland
18
  • Polythelia - accessory nipples(axillary region)
  • Polymastia -supernumerary brests
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