Lecture 4

• Respiratory System


  The system responsible for breathing and gas exchange in the body
• The various parts of the respiratory system


  • Trachea
  • Epiglottis
  • Larynx
  • Bronchus
  • Bronchioles
  • Alveoli
  • Diaphragm
• Organs of the respiratory system


  • Nose
  • Pharynx
  • Larynx
  • Trachea
  • Bronchi
  • Lungs - alveoli
• Air passage into the lungs

  1. Down a tube called the trachea

  2. Trachea made up of rings of cartilage

  3. Plates of cartilage at the top of the trachea widen at the "Adam's Apple"
• Adam's Apple

  The lump you can feel at the front of your throat, caused by the cartilage of the voice box (larynx)
• Alveoli


  • Give the lungs their spongy texture
  • Linings are very thin and need to be moist and clean to work well
• What happens when air is breathed in through the nose


  1. Filtered by hairs at entrance and by mucus

  2. Warmed by blood vessels passing close to nose lining

  3. Moistened by water vapour
• Breathing in


  1. Ribs lift upwards and outwards, caused by contraction of intercostal muscles

  2. Diaphragm contracts, changing from dome to flat sheet
• Breathing out

  Diaphragm relaxes, moving upwards back to dome shape
• Gaseous exchange

  • Alveoli in close contact with blood capillaries
  • Gas crosses respiratory membrane by diffusion
  • Oxygen enters blood, carbon dioxide enters alveoli
  • Macrophages add protection, surfactant coats gas-exposed alveolar surfaces
• Events of respiration


  • Pulmonary ventilation - moving air in and out of lungs
  • External respiration - gas exchange between pulmonary blood and alveoli
  • Respiratory gas transport - transport of oxygen and carbon dioxide via bloodstream
  • Internal respiration - gas exchange between blood and tissue cells in systemic capillaries
• Haemoglobin carries oxygen


  Attracts oxygen in the alveoli
• Oxygen is taken in


  Carbon dioxide is given out into the alveoli and then breathed out
• Respiratory system's main jobs


  • Get oxygen into the body
  • Get carbon dioxide out of the body
• Air we inhale contains 20% oxygen and 0.4% carbon dioxide
• Air we exhale contains 16% oxygen and 4% carbon dioxide
• Tidal volume


  The amount of air inspired and expired with each normal breath at rest or during exercise
• Vital capacity


  The largest amount of air that can be made to pass into and out of the lungs by the most forceful inspiration and expiration
• Oxygen debt


  Develops after about 5 minutes or more of constant exercise, when exercise becomes anaerobic (without oxygen) and has to be paid back later
• If exercise is just aerobic (with oxygen) there will be no oxygen debt
• Respiratory rate changes throughout life


  • Newborns - 40 to 80 respirations per minute
  • Infants - 30 respirations per minute
  • Age 5 - 25 respirations per minute
  • Adults - 12 to 18 respirations per minute
  • Rate often increases somewhat with old age