Skin Layers: Epidermis, Dermis & Hypodermis – Structure & Function

1. Epidermis (Outermost)

• Stratified squamous epithelium; avascular.
• Stratum corneum: Dead keratinocytes + keratin → barrier, waterproofing.
• Stratum basale: Stem cells, melanocytes (UV protection).
• Keratinocyte differentiation cycle ~28 days.

2. Dermis (Middle)

• Dense irregular connective tissue (collagen, elastin).
• Vascularized, innervated.
• Appendages: hair follicles, sebaceous/sweat glands.
• Functions: tensile strength, elasticity, thermoregulation, sensation, nutrient supply to epidermis.

3. Hypodermis / Subcutaneous Layer (Deepest)

• Adipose tissue (adipocytes) + loose connective tissue.
• Insulation, energy reserve, shock absorption, contour.
• Contains larger vessels/nerves traversing to skin.

Integrated Roles

Barrier, immunity, thermoregulation, sensation, vitamin D synthesis, psychosocial signaling.