• Why can't fish breathe in and out via ventilation?

  Water is denser, more viscous and has a lower oxygen content than air, so requires too much energy to be efficiently moved by a 2-way ventilation system
• Do prokaryotes need specialised exchange surfaces?

  No as they are small enough to get the resources they need via osmosis, diffusion etc.
• Why do larger, eukaryotic organisms need specialised exchange surfaces?

  Because they have greater metabolisms so need more resources and have lower SA:V ratios so cannot get all of these resources via simple diffusion, osmosis etc. as the substances need to travel further to get to our internal cells
• What are 4 things all good exchange surfaces should have/be?

  1. Large surface area

  2. Thin

  3. Good ventilation

  4. Good blood supply
• How does having a large surface area aid exchange surfaces?

  Allows more substances to travel across at a time, increasing exchange rate
• How does being thin aid exchange surfaces?

  Allows substances to travel across them more quickly, increasing exchange rate
• How does having a good blood supply aid exchange surfaces?

  Allows optimal concentration gradient to be maintained by bringing/taking away substances quickly
• How does having good ventilation aid exchange surfaces?

  Allows a steep concentration gradient to be maintained
• Why can a single-celled organism only reach a certain size?

  Because any larger and it's SA:V ratio would be too small for it to support its metabolism when only transporting materials via diffusion, osmosis etc.
• What is an exotherm?


  A cold-blooded organism
• What is an endotherm?

  A warm-blooded animal
• Why do mammals need excellent exchange surfaces?

  Because they have large metabolisms
• What is the exchange surface area of the lungs?

  Around 55-57 metres squared
• What is the biological name for the mouth?

  The buccal cavity
• What is the purpose of the nasal cavity?

  Increases the temperature and moisture content of inhaled air. It's hairy, mucus-secreting lining also traps pathogens and irritants
• What is the membrane on the surface of the lungs called?

  Pleural Membrane
• What are the muscles between the ribs called?

  Intercostal muscles
• What is the sequence of airways that air passes down?

  Mouth/Nostril--->Buccal/nasal cavity--->Trachea--->Bronchus--->Bronchioles--->Alveoli
• Which bones protect the chest cavity?

  The ribs
• Why does the trachea have c-shaped rings of cartilage?

  To prevent it from collapsing due to pressure changes in the lungs
• What two types of cells is the trachea lined by?

  Goblet and Ciliated Epithelial cells
• What is the purpose of goblet cells?

  They secrete mucus, which traps dust and microbes
• What is the purpose of ciliated epithelial cells?


  They are adjoining to goblet cells, and use their cilia to sweep mucus and whatever is trapped within it out into the throat
• What is the structure of the bronchi?

  Similar to the trachea and with rings of cartilage
• Which bronchioles have cartilage?

  Those with a diameter greater than 1mm
• What is the purpose of smooth muscle cells contained in the walls of the bronchioles?

  To allow them to dilate and constrict
• Are ciliated cells present in the bronchioles and alveoli?

  No
• Is gas exchange possible in the bronchioles?

  Some, through the flattened epithelial lining
• What is the diameter of alveoli?

  200-300 micrometers
• What are the walls of alveoli made up of?

  Squamous epithelial cells, some collagen and elastic fibres made from elastin
• What is the purpose of the elastic tissues in alveoli?

  They allow the alveoli to stretch when air enters, and recoil in order to help force air out
• Where is lung surfactant found?

  Coating the inside of alveoli
• What are the 2 purposes of lung surfactant?

  Prevent the alveoli from collapsing and help prevent water loss
• What is the purpose of external intercostal muscles?

  When they contract, they lift the ribcage up and out (during inhalation)
• What is the purpose of internal intercostal muscles?

  They push the ribcage downwards and inwards during forced exhalation
• What 2 steps occur during inspiration?

  1. Intercostals contract, making ribcage move upwards and outwards

  2. Around the same time, diaphragm contracts and flattens
• What effect does the movements of the diaphragm and intercostal muscles have during inspiration?

  Increases the volume of the chest cavity, causing its pressure to become lower than atmospheric pressure, meaning air moves into the lungs
• What 2 steps occur during expiration?

  1. The intercostal muscles relax, making the ribcage move downwards and inwards

  2. The diaphragm relaxes and expands into a dome shape
• What effect does the movements of the diaphragm and intercostal muscles have during expiration?

  They decrease the volume of the chest cavity, causing its pressure to increase to more than atmospheric pressure and, with the help of the recoil of the elastic fibres in the alveoli, forcing air out of the lungs
• What are 3 methods of measuring the volume of gas drawn into the lungs?

  1. A peak flow meter

  2. A vitalograph

  3. A spirometer