Integumentary System

• The skin is the biggest organ in the body
• Skin


  • Protects body against infection and extreme temperatures
  • Maintains fluid balance
  • Synthesizes vitamin D
  • Has nerve endings to sense the outside world
  • Has sweat glands and blood vessels to regulate temperature and communicate
• Integumentary system


  Includes skin, hair, nails, sweat and oil glands
• Skin has 3 layers: epidermis, dermis, and hypodermis
• Epidermis


  The outermost layer of skin that you can see
• Dermis


  The layer below the epidermis where most of the skin's functions occur
• Hypodermis


  The bottom layer of skin composed mostly of fat
• Epidermis

  • Made of keratinocytes that produce keratin
  • Constantly renewing itself, replaced every 4-6 weeks
  • Contains melanocytes that produce pigment
  • Contains Langerhans cells for immune defense
  • Contains Merkel cells for touch sensation
• Thick skin


  • Found on palms of hands and soles of feet
  • Has 5 layers of epidermis
• Thin skin


  • Covers rest of body
  • Has 4 layers of epidermis
• Epidermal layer penetration

  1. Stratum corneum (horny layer)

  2. Stratum lucidum (clear layer)

  3. Stratum granulosum (granular layer)

  4. Stratum spinosum (spiny layer)

  5. Stratum basale (basal layer)
• Dermis

  • Contains collagen and elastin fibers for strength and elasticity
  • Contains capillaries and blood vessels
  • Contains nerve fibers for sensation
  • Contains hair follicles, oil and sweat glands
• Papillary layer of dermis

  • Thin sheet of connective tissue with dermal papillae that form friction ridges (fingerprints)
• Reticular layer of dermis

  • Thicker layer of dense irregular connective tissue
• Hypodermis


  Layer of mostly fat tissue that provides insulation, energy storage, and anchors the skin
• Tattoos need to reach the dermis layer to be permanent
• Integumentary system


  The collection of resilient tissues, ranging from the sharp and hard to the soft and fluffy, that serve a whole panoply of functions
• Functions of the integumentary system

  • Protective barrier
  • Sensing the world
  • Excretion of waste
  • Blood storage
  • Temperature regulation
  • Vitamin D production
  • Indicating health issues
• The first and most vital purpose of the integumentary system is to act as a protective barrier
• Cutaneous sensory receptors


  Structures in the skin that are part of the nervous system and receive stimuli from the outside environment
• Tactile corpuscles


  Receptors that register the sense of touch
• Lamellar corpuscles


  Receptors that register the sense of pressure
• Hair follicle receptors


  Receptors that allow you to feel a slight breeze on your skin or through your hair
• Small amounts of nitrogen-containing wastes are eliminated through the skin in sweat
• Heavy sweating does not rid the body of toxins, it just results in the loss of more water
• Insensible perspiration


  The normal, barely noticeable sweat that oozes out about half a liter per day to regulate body temperature
• Sensible perspiration


  The noticeable sweat that can produce up to 12 liters per day during exertion to regulate body temperature
• When the body gets cold

  Dermal blood vessels constrict to conserve heat
• When the body warms up

  Dermal blood vessels relax to allow blood to return to the surface
• Cyanosis


  Blue skin indicating heart failure, poor circulation, or severe respiratory issues
• Jaundice


  Yellowing of the skin indicating liver disorder
• Erythema


  Reddened skin indicating fever, inflammation, or allergy
• Melanin


  The pigment produced by melanocyte cells that determines skin color and provides protection from UV rays
• Historically, higher concentrations of melanin provided an advantage in areas with intense solar radiation, while lower concentrations allowed for vitamin D production in areas with weaker sunlight
• Vitamin D


  The only vitamin the body can produce on its own by converting a molecule in the skin when exposed to UV light
• Cuticle


  The outermost layer of dead keratin protein cells on hair strands
• Hair shaft


  The part of the hair where keratinization is complete
• Hair root


  The part of the hair inside the follicle where keratinization is still happening
• Nail bed


  Where new nail cells divide at the root and get pushed forward, creating the scaly-hard keratin
• Types of sweat glands

  • Eccrine
  • Apocrine