Stratum lucidum
Epidermis · Layer 4 Palms and soles only Thick skin
A thin extra layer of densely packed, dead keratinocytes interposed between granulosum and corneum, present only in the thick skin of the palms and soles.
Detail
- Distribution
- Thick (glabrous) skin of the palms, soles and volar digits only; absent from thin skin everywhere else
- Contents
- Eleidin, a transitional product between keratohyalin and mature keratin
- Thick skin
- Has no hair follicles, sebaceous glands or arrector pili, but the highest density of eccrine glands in the body
- Consequence
- Because palmoplantar skin lacks pilosebaceous units, a deep burn there can only re-epithelialise from eccrine ducts and the wound margin
When it goes wrong
Palmoplantar keratoderma (inherited, or acquired with arsenic exposure or internal malignancy)
Thickened, fissuring palms and soles; fissures are painful and become portals for cellulitis
Absence of pilosebaceous units in thick skin
Acne never occurs on palms and soles, and topical drug absorption there is the poorest of any site — potent preparations are needed
Practise this structure
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