Mammalian

• Pathway taken by air in the mammalian gaseous exchange system


  Nasal cavity -> trachea -> bronchi -> bronchioles -> alveoli
• Function of the nasal cavity

  Good supply of blood which warms and moistens the air entering lungs

  Goblet cells in the membrane secrete mucus to trap dust and bacteria
• Goblet cells

  Goblet cells in the membrane secrete mucus to trap dust and bacteria
• Function and description of trachea

  Carries air to bronchi

  Lined by ciliated epithelium cells
• Description and function of bronchi

  Lined by ciliated epithelium cells

  Narrower than trachea

  Two for each lung

  Allow air to pass into the bronchioles
• Description and function of bronchioles

  Narrower than bronchi

  Only contain muscle and elastic fibres to contract and relax

  Allow passage of air into alveoli
• Description and function of alveoli

  Mini air sacks lined with epithelium cells

  Walls are only one cell thick

  Covered with a network of capillaries which facilitate gas diffusion
• Adaptations of alveoli for efficient gas exchange 


  ...
• Explain the process of inspiration and the changes that occur throughout the thorax

  EIM (EXTERNAL INTERCOSTAL MUSCLES) contract and IIM relax

  Ribs move up and out

  Diaphragm contracts and flattens

  Volume of thorax increases

  Air pressure outside of the lungs is higher than the air pressure inside

  Air is forced in
• Explain the process of expiration and the changes that occur throughout the thorax

  Ribs move down and in

  Diaphragm relaxes and domes

  Volume of thorax decreases

  Air pressure inside of the lungs is higher than the air pressure outside

  Air is forced out

  IIM contract and EIM relax
• What is tidal volume?

  The volume of air we breathe in and out during each breath at rest
• What is breathing rate?

  The number of breaths we take per minute
• How do you calculate pulmonary ventilation rate?

  Tidal volume x breathing rate

  Using a spirometer
• Describe and explain one feature of the alveolar epithelium that makes the epithelium well adapted for gas exchange

  Flattened cells/single layer of cells

  Reduces diffusion distance

  Permeable

  Allows diffusion of oxygen/CO2
• Suggest and explain how a reduced tidal volume affects the exchange of CO2 between the blood and the alveoli

  Less CO2 moves out of lungs/exhaled

  So reduces the diffusion gradient between blood and alveoli

  More CO2 stays in the blood
• Describe and explain the mechanism that causes the lungs to fill with air

  Diaphragm contracts and external intercostal muscles contract

  Volume increases and pressure decreases in lungs

  SO air moves down a pressure gradient
• Why might a scientist use haematoxylin solution and not iodine solution to stain lung tissue?

  Lung tissue does not contain starch

  Makes nucleus invisible
• Explain why the death of alveolar epithelium cells reduces gas exchange in human lungs

  Reduced SA

  Increases distance for diffusion

  Reduced RATE of gas exchange