gas exchange

• diffusion of O2 & CO2 occurs rapidly when:

  1. large surface area
  2. the distance in which diffusion will take place is small
  3. good blood supply
• large surface area: the presence of millions of alveoli in the lungs and branching filaments in the fish's gills providing a large space for gaseous exchange
• good blood supply: alveoli are surrounded by networks of blood capillaries
• thin epithelium: 2 layer cell first layer is the alveolus wall and the second is the capillary wall thus providing a shorter distance for diffusion
• ventilation: movement of fresh air into the lungs and stale air put of the lungs by inspiration and expiration
• 1. the trachea branches into 2 bronchi
  2. the bronchi branches into bronchioles
  3. the bronchioles end in the alveoli which are lined with capillaries for exchange
• function of the rib cage:

  1. protect the lungs and heart
  2. to move and ventilate the lungs
• inhaled air:

  1. nitrogen 79%
  2. oxygen 21%
  3. carbon dioxide 0.04%
• exhaled air:

  1. nitrogen 79%
  2. oxygen 16%
  3. carbon dioxide 4%