Dermatology: Structure of Epidermis & Dermis
The skin is composed of two primary layers: the epidermis (the protective barrier) and the dermis (the supportive, vascularized foundation).
1. The Epidermis (Avascular)
The epidermis is stratified squamous epithelium. From deep to superficial (mnemonic: Come Let’s Get Sun Burned):
- Stratum Corneum: Dead, keratinized cells (the barrier).
- Stratum Lucidum: Only in thick skin (palms/soles).
- Stratum Granulosum: Contains keratohyalin granules.
- Stratum Spinosum: Thickest layer; contains desmosomes (cell-to-cell bridges).
- Stratum Basale: Germinative layer where mitosis occurs.
2. The Dermis (Vascular)
| Layer | Characteristics |
|---|---|
| Papillary Dermis | Upper, thin layer; loose connective tissue, contains capillaries and Meissner’s corpuscles. |
| Reticular Dermis | Lower, thick layer; dense, irregular connective tissue, contains collagen bundles and elastin. |
High-Yield Exam Pearl:
- Desmosomes: Target of autoantibodies in Pemphigus Vulgaris, leading to suprabasal (intraepidermal) splitting.
- Hemidesmosomes: Target of autoantibodies in Bullous Pemphigoid, leading to subepidermal splitting (at the dermal-epidermal junction).
- Thickness: Skin is thickest on the back and thinnest on the eyelids.