integumentary

• Integumentary System


  The skin and its accessory structures

  
• Skin


  • Large waterproof covering
  • Provides UV light and chemical protection
• Accessory structures


  • Hair
  • Nails
  • Glands
• Epidermis


  Upper layer of the skin, composed of epithelial tissue divided into sublayers

  
• Dermis


  Lower layer of the skin, composed of dense connective tissue that connects the skin to fat and muscle

  
• Hypodermis


  Subcutaneous layer below the dermis, composed of fat
• Keratinization


  Cells move to surface, lose water, and nuclei change
• Layers of the Epidermis


  • Stratum corneum
  • Stratum lucidum
  • Stratum granulosum
  • Stratum spinosum
  • Stratum germinativum
• Stratum corneum


  • Outermost layer, composed of dead, keratinized cells
  • Barrier to light, heat, chemicals, and microorganisms
• Stratum lucidum


  • One to two cell layers thick
  • Flat and transparent
  • Difficult to see
• Stratum granulosum


  • Two or three layers
  • Flattened cells
  • Active keratinization
  • Lose nuclei
  • Compact and brittle
• Stratum spinosum


  • Several layers of spiny-shaped cells
  • Desmosomes prevalent
• Stratum germinativum


  • Rests on basement membrane
  • Lowermost layer called stratum basale
  • New cells produced here (mitosis)
  • Melanocytes produce melanin
• Structures found in the Dermis

  • Blood and lymph vessels
  • Nerves
  • Muscles
  • Glands
  • Hair follicles
• Divisions of the Dermis

  • Papillary
  • Reticular
  • Subcutaneous (hypodermis)
• Hair


  • Covers most of the surface of the body
  • Three parts: cuticle, cortex, medulla
  • Shaft: visible portion
  • Root: hair follicle
  • Arrector pili: smooth muscle
• Hair Growth


  1. Hair follicle

  2. Cycles of growth and rest
• Nails


  • Modified epidermal cells
  • Lunula: white crescent
  • Body: visible portion
  • Root: covered by skin
  • Growth occurs from the nailbed
• Sebaceous Glands


  • Produce sebum (oil)
  • Lubricates skin and hair
  • Secretion controlled by endocrine system
• Sweat Glands


  • Most numerous in palms and soles
  • Not found on margins of the lips or head of the penis
  • Each gland has secretory portion and excretory duct
  • Sweating helps cool the body
• Functions of the Integumentary System

  • Sensation
  • Protection
  • Thermoregulation
  • Secretion
• Sensation


  • Temperature receptors (hot and cold)
  • Pressure receptors (excessive pressure as pain, mild pressure as pleasurable)
  • Combinations produce burning, itching, tickling
• Protection


  • Prevents passage of harmful physical and chemical agents
  • Melanin protects from UV rays
  • Lipid content inhibits water loss
  • Acid mantle kills most bacteria
  • Nails protect ends of digits
  • Hair acts as insulation and filter
• Thermoregulation


  • Normal body temperature: 98.6 degrees F
  • When external temperatures increase: blood vessels dilate, sweat occurs
  • When external temperatures decrease: blood vessels first dilate then constrict
• Secretion


  • Sebum: cosmetic gloss, moisturizer, antifungal/antibacterial properties
  • Sweat: essential in cooling process
  • Vitamin D
• Dermis is also called corium