Human Skin

1. Epidermis (Outer Layer)

• Composition: Primarily made up of keratinocytes, which produce keratin (a protein that strengthens skin). It also contains melanocytes (responsible for pigment), Langerhans cells (immune response), and Merkel cells (touch sensitivity).
• Sub-layers:
  • Stratum Corneum: Outer layer of dead cells (corneocytes) that provide a tough, waterproof barrier.
  • Basal Layer: The deepest part of the epidermis, where new skin cells are produced.
• Functions:
• Protects against environmental damage (UV radiation, pathogens).
• Minimizes water loss through its lipid barrier.
• Determines skin color through melanin production.

2. Dermis (Middle Layer)

• Composition: Dense connective tissue containing collagen and elastin fibers, which give skin its strength and elasticity. It also houses:
  • Blood vessels
  • Nerve endings
  • Sweat and sebaceous (oil) glands
  • Hair follicles
• Functions:
  • Provides structural support.
  • Supplies nutrients to the epidermis.
  • Plays a role in thermoregulation via sweat glands and blood flow.
  • Hosts sensory receptors for pain, pressure, and temperature.

3. Hypodermis (Subcutaneous Layer)

• Composition: Composed mainly of fat (adipose tissue) and connective tissue.
• Functions:
  • Acts as an energy reserve.
  • Provides insulation and cushioning for underlying muscles and bones.
  • Facilitates skin mobility over the body.

Skin Functions

• Protection: Acts as a physical barrier to microorganisms, harmful chemicals, and physical trauma.
• Thermoregulation: Regulates body temperature through sweating and blood vessel dilation/constriction.
• Sensation: Detects touch, pressure, pain, and temperature changes through specialized nerve endings.
• Excretion: Removes waste products like salts and urea through sweat.
• Vitamin D Synthesis: Produces Vitamin D when exposed to sunlight.
• Immunity: The epidermis and dermis house immune cells that help fight infections.

Factors Influencing Skin Health

• Genetics: Determines traits like skin color, type (oily, dry, etc.), and susceptibility to conditions.
• Age: Skin loses elasticity, becomes thinner, and regenerates slower with age.
• Environment: Sun exposure, pollution, and climate can damage or alter skin.
• Lifestyle: Nutrition, hydration, sleep, and skincare routines impact skin's appearance and function.