Lecture on the Integumentary System

Introduction

• Common associations with "organ" often overlook the skin.
• Skin is the largest organ of the body.
  • Functions:
    • Protection against infection and extreme temperatures.
    • Fluid balance maintenance.
    • Vitamin D synthesis.
    • Sensation with nerve endings.
    • Temperature regulation via sweat glands and blood vessels.
  • Accounts for 3-5 kg of body weight, covers up to 2 square meters.
  • Forms the integumentary system with hair, nails, sweat, and oil glands.

Structure of Skin

• Three Main Layers:
  • Epidermis:
    • Visible outer layer made of stratified squamous epithelial tissue.
    • Contains keratinocytes (keratin production), melanocytes (melanin production), Langerhans cells (immune response), Merkel cells (touch receptors).
    • Thick skin (palms, soles) has 5 layers, thin skin has 4.
  • Dermis:
    • Below the epidermis, involved in sweating, blood circulation, and sensation.
    • Contains collagen and elastin fibers for strength and elasticity, as well as capillaries, nerve fibers, hair follicles, and glands.
    • Comprises two layers: papillary (areolar connective tissue, forms fingerprints) and reticular (dense connective tissue).
  • Hypodermis (Subcutis):
    • Consists mostly of adipose tissue.
    • Provides insulation, energy storage, shock absorption, and anchors skin.

Functions and Characteristics

• Epidermis:
  • Keratinocytes make up most of the epidermis.
  • Skin color determined by melanocytes, which have similar numbers across all humans but differ in cellular extensions and melanin content.
  • Defensive role with Langerhans cells ingesting invaders.
  • Merkel cells for touch sensation.
• Dermis:
  • Houses dynamic elements like nerve fibers and blood vessels.
  • Tattoos penetrate to the dermis.
• Hypodermis:
  • Major site for body fat.

Miscellaneous

• Epidermis is avascular; nutrients and oxygen come from dermis.
• Damage to skin layers can lead to serious complications.
• Importance of sunscreen to prevent UV damage and skin cancer.

Conclusion

• Overview of skin structure, mechanism, and function.
• Brief mention of upcoming topics such as lotions, deodorants, and hair care.

Credits

• Written by Kathleen Yale, directed/edited by Nicholas Jenkins.
• Contributions by Blake DePastino, Dr. Brandon Jackson, Michael Aranda, and Thought Cafe.

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• Remember: "Come, Let's Get Sunburned" mnemonic for epidermal layers.
• Importance of hydration and care for skin health.