Lecture Notes: The Integumentary System - Skin

Introduction to Skin

• Often overlooked as an organ despite being the body's largest
• Functions include:
  • Protection against infection and temperature extremes
  • Fluid balance maintenance
  • Vitamin D synthesis
  • Sensory perception through nerve endings
  • Thermoregulation and communication via blood vessels and sweat glands
• Characteristics:
  • Accounts for 3-5 kg of body weight
  • Covers up to 2 square meters if spread out
  • Has insulating, waterproof, and self-repairing properties

Composition of the Integumentary System

• Includes skin, hair, nails, sweat, and oil glands
• Layers: Epidermis, Dermis, and Hypodermis (Subcutis)

Layers of the Skin

1. Epidermis

• Visible layer of skin
• Made of stratified squamous epithelial tissue
• Major cell types:
  • Keratinocytes: Building blocks for keratin, contribute to skin's waterproofing and durability
  • Melanocytes: Produce melanin, determining skin color but not in number, rather in the extent of their cellular extensions
  • Dendritic/Langerhans Cells: Immune cells originating from bone marrow
  • Merkel Cells: Tactile receptors
• Thick vs. Thin Skin:
  • Thick skin: 5 layers found on palms and soles
  • Thin skin: 4 layers covering the rest of the body

2. Dermis

• Functional layer where most skin activities occur
• Contains collagen, elastin fibers, capillaries, blood vessels, nerve fibers, hair follicles, and glands
• Layers:
  • Papillary Layer: Areolar connective tissue with dermal papillae, forms fingerprints
  • Reticular Layer: Dense irregular connective tissue

3. Hypodermis (Subcutis)

• Composed mostly of adipose tissue
• Functions: Insulation, energy storage, shock absorption, skin anchoring

Skin Interactions and Health

• Sun damage and the importance of sunscreen
• Immune response in the epidermis
• Tattoos and their permanence related to dermal penetration
• Future topics: Efficacy of lotions, deodorants, and hair care

Conclusion

• Overview of skin's structure and function
• Importance of skin care and protection
• Acknowledgments to contributors and supporters of the educational content

Further Reading

• Upcoming discussions on skin care products and their effectiveness.