The Respiratory System

• Respiratory system


  A specialised system needed to ensure enough oxygen can get into the body for respiratory requirements
• Respiratory system in humans and many other animals

  • Bronchiole
  • Intercostal muscles
  • Larynx
  • Ring of cartilage supporting trachea
  • Trachea
  • Left lung
  • Left bronchus
  • Heart
  • Diaphragm
• The pleural fluid between the pleural membranes helps to reduce friction between the lungs and between the lungs and the chest wall
• Breathing brings fresh air, rich in oxygen into the body
• The respiratory system is specialised for efficient gas exchange with the external environment
• The respiratory system is designed to deliver oxygen to a surface where it can be absorbed, and taken to cells to be used in respiration
• Waste products e.g. carbon dioxide and water need to be delivered back to the respiratory surface and removed
• Structure of the respiratory system


  • Air is warmed and filtered in the nasal cavity before reaching the trachea
  • Consists of a series of tubes: Nasal passages, trachea, bronchi and bronchioles, which carry the air gases to and from the lungs
  • The trachea stays open during the pressure changes (inhaling and exhaling) as it has c-shaped (incomplete) rings of cartilage in its walls
  • The nasal passages are lined with ciliated epithelial cells (have hairs) that make mucus and trap micro-organisms, to filter and heat the incoming air
• Pleural membranes


  • Line the inside of the chest wall (the ribs) and also the outside of the lungs
  • Reduce friction during breathing as the lungs fill with air and deflate
  • The space between the pleural membranes in the pleural cavity contains a small amount of pleural fluid which helps to further reduce friction during breathing
• Alveoli


  • At the ends of the bronchiole tubes
  • This is where gas exchange takes place between the atmosphere and the blood
  • Oxygen diffuses into the blood from the alveoli and carbon dioxide goes the other way, diffusing from the blood into the alveoli, where it is breathed out
• Thorax pressure falls


  Air decreases