Describe the basic structure of the skin:
Epidermis: 5 layers of keratinocytes
keratin: hard protein linked by desmosomes
What are the 5 basic functions of the skin?
Protection Sensation Thermoregulation Excretion Vitamin D Synthesis
How is the skin used for protection?
– mechanical trauma; pathogens (skin pH, antimicrobial substances, immune cells), environment (UV)
How is the skin used for sensation?
– sensors to nervous system
How is the skin used for thermoregulation?
– feedback loops for increasing or decreasing temperature (blood vessels constrict or dilate; sweat
glands for heat)
How is the skin used for excretion?
– lactic acid, urea, metals
How is the skin used for Vitamin D?
Vitamin D synthesis (Vitamin D precursor in skin + UV light – Cholecalciferol (D3)
Describe how the cells of the epidermis are arranged into layers:
- stratum corneum
- stratum lucidum
- stratum granulosum
- stratum spinosum
- stratum basale
Describe the cells of the stratum corneum:
- top/outermost layer, 20-30 layers of dead keratinocytes
Describe the cells of the stratum lucidum:
- Only in thick skin—narrow clear layer of dead keratinocytes
Describe the cells of the stratum granulosum:
- 3-5 rows of cells. Granules contain keratin bundles or lipid based lamellar granules
Describe the cells of the stratum spinosum:
- “prickle cells” Keratinocytes + desmosomes filaments + pre-keratin (several layers)
Describe the cells of the stratum basale:
- single layer of metabolically active stem cells (may appear cuboidal/columnar)
Differentiate between thick and thin skin:
- Thick skin: palms and soles
All 5 strata (including lucidum)
Has sweat glands, but no hair - Thin skin: everywhere else
No stratum lucidum
Hair, sebaceous and sweat glands
(eccrine and apocrine)
