Human Skin: Layers, Surface Area & Regional Differences

Adult skin covers ~1.8–2 m² (19–22 ft²) and comprises three layers:

1. Epidermis (outermost)

• Stratified squamous epithelium; keratinocytes produce keratin for barrier function.
• Melanocytes → melanin (UV protection, pigment).
• Langerhans cells → immune surveillance.

2. Dermis (middle, thickest)

• Connective tissue (collagen, elastin) for strength/elasticity.
• Vasculature, hair follicles, sweat & sebaceous glands, nerve endings.
• Thermoregulation, sensation, nutrient supply.

3. Hypodermis / Subcutaneous Layer

• Adipocytes (fat) for insulation, energy storage, shock absorption.

Regional Variations

• Face/scalp: Thin, sebaceous-rich, UV-exposed.
• Torso: Thicker, less wrinkle-prone.
• Limbs: Thinner, prone to dryness.
• Palms/soles: Thick stratum corneum, no hair, high tactile sensitivity.