Integumentary

• The integumentary system consists of the skin and accessory structures, such as hair, glands, and nails

  
• Integumentary System


  • Forms the boundary between the body and the external environment, thereby separating us from the external environment while allowing us to interact with it
• Major functions of the integumentary system

  • Protection
  • Excretion
  • Sensation
  • Temperature regulation
  • Vitamin D production
• Excretion


  Small amounts of waste products, such as urea, uric acid, and ammonia, are excreted through the skin and glands
• Sensation


  Acts as sense organ; has sensory receptors that can detect heat, cold, touch, pressure, and pain
• Vitamin D production


  When exposed to ultraviolet light, the skin produces a molecule (7-dehydrocholesterol) that can be transformed into vitamin D, an important regulator of calcium homeostasis
• Layers of the skin

  • Epidermis
  • Dermis
  • Hypodermis (Subcutaneous tissue)

  
• Keratinocytes


  Predominant cells in the epidermis; contain keratin filaments in their cytoplasm
• Layers of the epidermis

  • Stratum Germinativum (Basale)
  • Stratum Spinosum
  • Stratum Granulosum
  • Stratum Lucidum
  • Stratum Corneum
• Layers of the dermis

  • Papillary Layer
  • Reticular Layer

  
• The integumentary system includes the epidermis, dermis, hypodermis, glands, hair, and nails.
• The integumentary system also has a barrier function that regulates body temperature, maintains cell fluid, synthesizes vitamin d, and detects the stimuli.
• The most obvious function of the integumentary system is the protection the skin gives to underlying tissues.
• The skin keeps the most harmful substances out and prevents the loss of fluids.
• In protection, the intact skin reduces water loss because its lipids act as a barrier to the diffusion of water.
• The skin prevents microorganisms and other foreign substances from entering the body.
• Secretion from skin glands also produces an environment unsuitable for some microorganisms.
• The stratified squamous epithelium of the skin protects underlying structures against abrasion.
• What skin structure protects the underlying structures against abrasion?

  Stratified squamous epithelium
• What does the stratified squamous epithelium of the skin protect?

  Underlying structures
• What does the stratified squamous epithelium of the skin protect the underlying structures from?

  Abrasion
• What absorbs ultraviolet light and protects underlying structures from its damaging effects?

  Melanin
• Melanin absorbs ultraviolet light and protects underlying structures from its damaging effects.
• The hair on the head acts as a heat insulator.
• Eyebrows keep sweat out of the eyes.
• Eyelashes protect the eyes from foreign objects.
• Hair in the nose and ears or cilia prevent the entry of dust and other materials.
• The nails protect the ends of the fingers and toes from damage.
• The nails can be used in defense for the fingers and toes.
• Waste products are eliminated through gland secretions in a process called excretion.
• The skin is a sense organ.
• The skin detects heat, cold, touch, pressure, and pain in the process of sensation.
• When exposed to UV, the skin produces 7-dehydrocholesterol to produce vitamin D.
• Vitamin D is important in calcium regulation.
• 7-dehydrocholesterol turns to cholecalciferol or vitamin D3.
• Vitamin D3 turns to 25-hydroxyvitamin D (calcidiol) in the liver.
• 25-hydroxyvitamin D (calcidiol) turns to 1,25-dihydroxyvitamin D (calcitriol)
• The amount of blood flow beneath the skin surface and the activity of sweat glands contribute to temperature regulation.
• Blood vessels = dilate = hot
• Blood vessels = constrict = cold