## Histological Features of Deep Partial-Thickness Burns **Key Point:** Deep partial-thickness (2nd degree) burns destroy the epidermis and extend into the dermis, but crucially preserve dermal appendages (hair follicles, sweat glands) in the deeper dermal layers, allowing for re-epithelialization. ### Burn Depth Classification | Burn Depth | Skin Layers Involved | Histology | Healing | |---|---|---|---| | **Superficial (1st)** | Epidermis only | Epidermal necrosis, intact basal layer | Spontaneous, no scar | | **Superficial Partial (2nd)** | Epidermis + superficial dermis | Epidermal destruction, upper dermal damage, intact deep dermal structures | Spontaneous in 2–3 weeks | | **Deep Partial (2nd)** | Epidermis + upper-to-mid dermis | Extensive dermal necrosis BUT preserved dermal appendages in deep dermis | Slow healing, hypertrophic scarring | | **Full-Thickness (3rd)** | All skin layers + subcutaneous | Complete charring, no viable cells, dermal appendages destroyed | Requires grafting | | **Subdermal (4th)** | Extends to muscle/bone | Carbonization, tissue destruction beyond skin | Requires extensive grafting/amputation | **High-Yield:** The presence of intact dermal appendages (especially hair follicles and sweat glands in the deep dermis) is the hallmark that distinguishes deep partial-thickness from full-thickness burns and indicates potential for spontaneous healing, albeit with significant scarring. **Clinical Pearl:** Deep partial-thickness burns appear mottled red or white, are painless (nerve endings destroyed) or minimally painful, and do not blanch. They heal slowly (3–8 weeks) with hypertrophic scarring and contracture formation. **Mnemonic:** **DEEP 2nd = Dermis Extensively Exposed but Preserved appendages** — the dermal appendages survive in the deepest layers, allowing slow re-epithelialization from the edges and depths.
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