Layers of the Epidermis

Layers of the Epidermis

1. Stratum Corneum (20-25 layers)

   • Layers of keratinocytes
     • Containment
     • Water protection
     • 28 day cycle
       • 14 to reach SC
       • 14 to be shed
     • No nucleus
   • Squaemous Epithelium

2. Stratum Granulosum

   • Contains increasingly kertainised cells
     • Keratin organises into fibres
   • Lamellar granules produce lipid 'glue
   • Some undergo apoptosis
     • They're too far from a nutrient source
   • Nuclei being to disintegrate

3. Stratum Basale

   • Basal Cells
     • Rapidly dividing
     • Keratinocytes
   • Merkel Cell
     • Associated with sensory nerves
       • Shapes/textures
     • Found at bottom of sweat duct
   • Melanocytes
     • 8-10% of stratum basale
       • Produce melanosomes
     • Apoptosis of these cells under UV causes sunburn

4. Stratum Spinosum

   • Adjacted cells bonded by desmosomes
   • Coarser keratin than in the stratum basalum
   • Limited ability to divide
   • Langerhans Cell
     • Presents antigens of taken up microbes
       • So T-cells will recognize them

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