Mammalian gas exchange

• What is the need for exchange systems?

  All organisms need to oxygen and other nutrients to survive but they also need to remove the waste products so they dont build up and become toxic
• What are the three factors that affect exchange systems?

  Size

  Surface area to volume ratio

  Level of activity
• What are the features of a good exchange system?

  Large surface area: provides more space for molecules to diffuse, often achieved by the folding of membranes and walls

  Thin barrier: reduces the diffusion distance

  Good blood supply: important to maintain a steep concentration gradient so diffusion can occur rapidly
• Structure and function of the trachea?

  There are C - shaped cartilage rings for support

  Lined with ciliated epithelium cells and goblet cells, goblet cells make thick mucus which is swept up the trachea but the ciliated epithelial cells

  There is smooth muscle within the walls of the trachea that contract if there are any harmful substances detected as the contracting reduces airflow into the lungs
• Bronchi and bronchioles structure and functions?

  The trachea splits into the bronchi and the bronchi splits into branches called the bronchioles.

  They are both also lines with ciliated epithelium and goblet cells.

  They also have cartilage rings to prevent collapse during inspiration
• Structure and function of the alveoli?

  Alveoli is the site of gas exchange, O2 from the alveoli diffuses into the blood and CO2 from the blood diffuses into the alveoli to be exhaled

  The alveoli has a large surface area because there is a very large number of alveoli in the lungs

  The alveoli walls are very thin as it is made of squamous epithelial cells so there is a short diffusion distance

  Each alveolus is surrounded by a network of capillaries providing a good blood supply and maintaining a concentration gradient
• Ventilation?

  Ventilation is the mechanism of breathing and it consists of inspiration and expiration
• What happens during inspiration?

  The diaphragm muscle contracts causing it to move down and the intercoastal muscles contract causing the ribs to move up and out. This causes the volume inside the lungs to increases the the pressure to decrease, causing airflow into the lungs
• What happen during expiration?

  The diaphragm muscle relaxes causing the diaphragm to move up. The intercoastal muscle relaxes causing the ribs to move in and down. This causes the volume in the lungs to decrease and the pressure in the lungs to increases causing airflow out of the lungs
• Using a spirometer?


  Measures lung volumes by measing the the movement of air in and out of the lungs as a person breathes
• Precautions that must be taken when using a spirometer?

  The subject must be healthy

  The soda lime should be fresh and functioning

  The mouthpiece should be sterilised after every use

  There should be no air leaks in the apparatus

  The water chamber must not be overfilled
• Lung volume measurements?

  • vital capacity: the maximum volume of air that can be moved by the lungs in one breath, breathing in as much air as possible and breathing out as much as possible
  • Residual volume: volume of air that is left in the lungs after forced expiration
  • Tidal volume: volume of air moved in and out of the lungs with each breath at rest
  • Total lung capacity: total volume of air in the lungs
• Measuring oxygen uptake?

  Measure the difference in volume between the two points, divide by the time taken for this decrease