Skin Layers

Epidermis

• Stratum Corneum
  • Horny, Keratin Layer
• Stratum Lucidum
  • Seen with thick horny layer (palms & soles)
• Stratum Granulosum
  • Granular Layer
• Stratum Spinosum
  • Prickle, Spiny Layer
  • Langerhans Cells: Function as macrophage of the epidermis and process contact antigens
• Stratum Germinativum
  • Basal cell layer

• • Basal Cell Keratinocyte: only cell of the epidermis capable of division.
    • They divide and migrate upward.
    • Total turnover time is 28 days (14 days of migration and 14 days to be discarded)
  • Melanocyte: Produces malanin which is transferred to keratinocytes.
    • Melanin protects the skin from UV Radiation.
    • In whites, found mostly in basal cell layer.
    • In blacks, found throughout the epidermis.

Dermal-Epideramal Junction (Basement Membrane)

• Lamina Lucida
• Lamina Densa
• Sublamina Densa

Dermis

• Papillary Dermis: Immediately beneath epidermis.
  • Thin haphazardly arranged collage fibers, abundant ground substance, and delicate elastic fibers
• Reticular Dermis: extends to the subcutanous fat.
  • Coarse elastic fibers and thick collagen bundles arranged mostly parallel to skin surface

 

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Skin Structures

Hair Follicle

• Hair growth proceeds through distinct phases
  • Anagen: prolonged growth
  • Catagen: short lived interphase
  • Telogen: final resting phase
• Cells of hair bulb produce hair shaft which is completely keratinized and has no living cells.
• Hair color is due to the amount and type of melanin.

Eccrine Glands

• Found in highest concentration on palms, soles, and axillae.
• Secretory coil located in dermis, transmits sweat directly to skin surface for cooling of body

Apocrine Glands

• Found primarily in axillae and anogenital regions and serves as a scent gland.
• derived from hair germ and opens directly into pilosebaceous follicle rather than skin surface.
• Become active at puberty

Sebaceous Glands

• Found on all body parts except palms and soles
• Produces oil (sebum) that is emptied into the hair follicle.
• Lubricates and protects the hair and skin

Arrectores Pilorum

• Smooth muscle attached to the base of the hair follicle
• Contract in response to cold or fright
• "goose bumps"

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