Integumentary System and Skin

Introduction

• Skin is the largest organ, part of the integumentary system.
• Functions of skin:
  • Critical for homeostasis: maintaining body temperature and fluid balance.
  • Acts as a physical barrier: protects internal structures and organs.
  • Produces Vitamin D.
  • Has sensory functions.

Layers of the Skin

1. Epidermis

• Keratinocytes: Cells that produce keratin, making skin water-resistant and tough.
• Cornified Cells: Hardened, dead cells full of keratin located at the surface.
• Mnemonic for Epidermis Layers: "Can lemurs get some bamboo?"
  • Stratum Corneum: Outermost layer, consists of dead cornified cells.
  • Stratum Lucidum: Found in thick skin areas (palms, soles), transparent cells.
  • Stratum Granulosum: Contains granules and keratinocytes flatten here.
  • Stratum Spinosum: Contains keratinocytes and cells that act like macrophages.
  • Stratum Basale: Deepest layer, where basal cells and melanocytes are found.

2. Dermis

• Contains blood vessels, sweat glands, hair follicles, and nerves.
• Two layers:
  • Papillary Layer: Loose connective tissue.
  • Reticular Layer: Dense connective tissue.
• Fibroblasts: Produce collagen and elastin proteins.

3. Hypodermis

• Connects skin to underlying bone and muscle tissue.
• Contains adipose tissue for insulation.

Accessory Structures

• Sweat Glands: Assist in temperature regulation through evaporation.
• Sebaceous Glands: Produce oil to waterproof and lubricate skin and hair.
• Hair: Grows from hair follicles in the dermis.
• Nails: Protects fingers and toes, grows from mitotically active cells.

Importance of Studying the Integumentary System

• Skin cancer is the most common cancer in the US:
  • Basal Cell Carcinoma: Arises from basal cells.
  • Melanoma: Arises from melanocytes.
  • Merkel Cell Carcinoma: Rare, aggressive cancer.
• Understanding the integumentary system aids in treating skin cancers.

Burns and Their Impact

• Burns classified by degree based on layers affected:
  • First Degree: Affects epidermis.
  • Second Degree: Affects epidermis and part of dermis.
  • Third Degree: Affects epidermis and all dermis.
  • Fourth Degree: Extends to bones and muscles.
• Burns compromise skin functions and increase infection risk.
• Specialized medical personnel are trained to treat burns.

Conclusion

• The integumentary system's critical role in protection and homeostasis.
• Encouragement to continue exploring and learning about this system.