respiratory system

• Respiration


  A process that occurs in practically all living cells, using oxygen as a vital ingredient to free energy from food
• Respiration

  1. Oxygen from atmosphere enters body

  2. Oxygen and carbon dioxide exchanged between air and blood

  3. Carbon dioxide removed from body
• Respiratory system


  • Facilitates the exchange of gases (CO2 and O2) between the air we breathe and our blood through breathing
• Passage of air from nose to lungs

  1. Air enters nose

  2. Passes through nasal cavities, warmed, moistened and filtered

  3. Passes through pharynx (throat)

  4. Enters trachea (windpipe)

  5. Divides into right and left bronchi

  6. Bronchi branch into bronchioles

  7. Bronchioles terminate in alveoli (air sacs)
• Alveoli

  • Walls are extremely thin, with a network of capillaries surrounding each like a string bag
  • Where oxygen from air is exchanged for carbon dioxide from bloodstream
• Breathing

  1. Inspiration (air movement from atmosphere into lungs)

  2. Expiration (air movement from lungs to atmosphere)
• During inspiration

  Diaphragm contracts and flattens, external intercostal muscles lift ribs outwards and upwards, increasing chest cavity volume and decreasing air pressure in lungs, causing air to rush in
• During expiration

  Diaphragm relaxes and moves upwards, internal intercostal muscles allow ribs to return to resting position, decreasing chest cavity volume and increasing air pressure in lungs, causing air to be forced out
• Normal resting breathing rate is approximately 12 to 18 breaths per minute
• Breathing rate can increase with physical activity, excitement or elevated body temperature, and changes with age
• Gaseous exchange


  Two-way diffusion of oxygen and carbon dioxide between air in alveoli and blood in surrounding capillaries
• Oxygen moves from air in alveoli into blood, where it attaches to haemoglobin in red blood cells
• Carbon dioxide moves from blood into alveoli to be breathed out
• Gaseous exchange also occurs between blood in capillaries and cells of the body, with oxygen unloaded to cells and carbon dioxide given up to blood
• During physical activity

  Respiratory system responds with increased rate and depth of breathing to deliver more oxygen to blood and remove wastes
• Increased rate and depth of breathing


  Provide greater ventilation and occur in proportion to increases in exercise effort