Dermis & Subcutaneous Layer
While the epidermis provides a barrier, the dermis and subcutis provide structural support, nutrient delivery, and thermoregulation.
Layers & Composition
| Layer | Key Characteristics |
|---|---|
| Papillary Dermis | Superficial; loose connective tissue, capillary loops, and Meissner’s corpuscles. |
| Reticular Dermis | Deep, dense irregular connective tissue; thicker collagen bundles; hair follicles, glands. |
| Subcutis (Hypodermis) | Adipose tissue: insulation, energy storage, shock absorption. |
Key Cellular & Structural Components
- Fibroblasts: The primary cells of the dermis; synthesize collagen (Type I), elastin, and glycosaminoglycans (GAGs).
- Collagen: Provides tensile strength; Type I is predominant in the adult dermis.
- Elastin: Provides elasticity and recoil; loss of elastin contributes to photoaging and wrinkles.
High-Yield Exam Pearl:
- Photoaging: UV radiation triggers matrix metalloproteinases (MMPs), which degrade collagen and elastin, leading to a loss of skin tone.
- Panniculitis: Inflammation of the subcutaneous fat. Think Erythema Nodosum (septal panniculitis) when you see tender nodules on the shins, often associated with systemic triggers like infections or inflammatory bowel disease.