The Respiratory system

Published on 4th April 2018


  • Uptake of oxygen by all cells for energy production 
  • Formation of carbon dioxide and water as waste products 
  • Exchange of these gases occurs between: 
    • the alveoli of lungs and blood capillaries – external respiration 
    • blood capillaries and all cell walls – internal respiration 


  • Nasal passages 
  • Pharynx 
  • Larynx 
  • Trachea 
  • Bronchi 
  • Bronchioles 
  • Alveoli 
  • Pleura 
  • Diaphragm 
  • Thoracic cavity 



  •  Intercostal muscles contract. Ribs move up and out 
  • Diaphragm contracts and flattens. Lungs pulled downwards 
  • Chest Cavity enlarges – so pressure inside chest is lowered and air is sucked in 


  • Intercostal muscles and diaphragm relax 
  • Chest cavity decreases in size – so pressure inside chest is increased and air is forced out 



  • Normal rate about 16 x minute 
  • Controlled by chemo receptors in aorta and carotid arteries which monitor levels of gases in blood and send information back to brain 
  • Amount of lung expansion and muscle activity are also monitored by the brain


Additional Information for VTCT Qualification

The nose is separated into 2 nostrils by a plate of cartilage called the septum. There are specialised cells in the roof of the nose 
which are stimulated when chemical particles dissolve in the moist mucosal lining as we inhale. Nerve fibres travel from here 
towards the special olfactory area of the temporal cortex of the brain where the impulses are interpreted and we become aware 
of the smell. 
If the smell is one we perceive as pleasant it may increase our appetite and so can play an important role in the digestive 
process. Our ability to smell also influences our sense of taste as found when we have a cold! Our sense of smell is a primitive one 
and would have been vital to our survival in the past just as it is for wild animals .It also links directly with the emotional part of 
the brain and so can evoke powerful memories.


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