Chapter 10 skin pt 1

Skin Functions

• Protection: Skin acts as a barrier to prevent damage from outside elements, such as heat or pathogens.

  • Example: Touching a hot oven can cause burns, but receptors in the skin signal to move away.

• Flexibility: Skin is elastic and stretchy, allowing it to adapt to body changes and injuries.

• Excretion: Skin helps eliminate small amounts of water, salts, and waste products (urea, ammonia, uric acid) through sweat, which is crucial for maintaining electrolyte balance during physical activity.

• Vitamin D Synthesis: Exposure to ultraviolet (UV) light helps produce vitamin D, essential for regulating calcium and phosphorus in the blood, vital for bone health.

  • Rickets: Lack of vitamin D leads to softening and potential deformities in bones due to inadequate mineralization.

• Immunity: Skin contains immune cells that protect against bacteria and microorganisms, especially around potential injury sites.

Homeostasis

• Body Temperature Regulation: The body maintains homeostasis by balancing heat production and loss, primarily through the skin.

  • 80% of heat loss occurs via the skin, while the remaining 20% is through other systems like respiration and digestion.

  • Feedback Loop:

    • When exercising, body temperature rises (typically around 98.6°F/37°C).

    • Receptors in the skin detect temperature changes and notify the hypothalamus.

    • To cool down, blood vessels dilate, increasing blood flow to the skin and activating sweat glands for heat dissipation.

  • Cold Environment Response: In cold situations, the body constricts blood vessels to retain heat, potentially leading to frostbite in extremities (fingers, toes, nose).

Skin Structure

• Layers of Skin: The skin consists of the epidermis and dermis, with the hypodermis (subcutaneous layer) not technically part of the skin.

  • Epidermis: Thin, outer layer visible on the surface.

  • Dermis: Thicker layer beneath the epidermis containing blood vessels, nerves, sweat glands, sebaceous glands, hair follicles, and connective tissue (collagen, elastin).

  • Hypodermis: Fatty layer beneath the dermis that provides insulation and cushioning.

  • Dermal-Epidermal Junction: The connection between the epidermis and dermis, critical for skin integrity. Issues here can lead to blisters.

• Thick vs. Thin Skin:

  • Thick Skin: Has 5 layers and is found on the soles of feet and palms of hands (hairless).

  • Thin Skin: Has 4 layers and covers the rest of the body.