INTEGUMENTARY

• Components of integumentary system


  Skin

  • Comprised of three layers; epidermis, dermis, subcutaneous layer

  Accessory organs

  • Hair follicles
  • Exocrine glands; sebaceous glands, sweat glands
  • Melanocytes
• Skin - epidermis

  • Strong surface layer
  • Made up of squamous epithelial cells which wear away over time
  • Regenerated by stem cells in the lower layer of the epidermis
  • No vasculature therefore gains nutrients from underlying layers
  • Contains keratin which aids waterproofing of epidermis
• skin - dermis

  • layer of connective tissue to support epidermis and elasticity of the skin
  • contains vasculature and nerve endings
  • also has hair follicles and exocrine glands
  • melanocytes border epidermis/dermis and is responsible for skin pigmentation
  • divided into two layers; papillary and reticular
• Hair

  • Made up of keratin protein
  • Grows upwards and outwards from hair follicles
  • Located within dermal layer
• sweat glands

  • release sweat when temperature rises
  • thermal energy from skin and blood capillaries close to skin surface are transferred to the water in sweat, causing it to evaporate
  • transfer of thermal energy cools the skin
• blood vessels


  Vasoconstrict or vasodilate depending on the conditions
• Temperature regulation

  1. Core temperature falls sending nerve impulses from temperature receptors in hypothalamus to arterioles
  2. Causes contraction of muscles within arteriole walls
  3. Causes vasoconstriction of blood vessels
  4. Less blood flows through capillaries close to surface
  5. Blood is diverted through shunt vessels to venule meaning less thermal energy is transferred by radiation
• hairs

  • fall in temperature causes the hypothalamus to send nerve impulses to hair erector muscles
  • causes contraction of muscles and raises hair
  • this thickens the layer of air trapped next to the skin, forming an insulative layer
  • When temperature rises, signals are sent to relax these muscles causing the hair to lie flat, reducing the thickness of the insulative layer
• shivering

  • reflex action involving small rapid contraction of skeletal muscles
  • energy used in this process generates heat which is used to raise core body temperature
  • temperature receptors in skin send these signals to the hypothalamus causing the mechanism of shivering