Gas exchange

• definition of breathing ?

  movement of air into and out of the lungs
• definition of respiration ?

  a chemical reaction that releases energy in the form of ATP
• what are the key structures in human gas exchange?

  alveoli

  bronchioles

  bronchi

  trachea

  lungs
• what are the muscles around the ribs called?

  intercostal muscles (internal & external)
• what happens when the external intercostal muscles contract?

  the ribs move up & out leading to inspiration
• what happens when the internal intercostal muscles contract?


  the ribs move down & in leading to expiration
• describe inspiration?

  -external intercostal muscles contract & the ribs move up and out.

  • internal intercostal muscles relax
  • the diaphragm contracts moving down
  • increasing the volume of the thorax
  • decreasing pressure inside the thorax
  • air moves in, down a pressure gradient.
• describe expiration?

  -external intercostal muscles relax

  • internal intercostal muscles contract & the ribs move down and in.
  • the diaphragm relaxes & domes upwards.
  • causing a decrease in thorax volume.
  • increasing pressure inside the thorax.
  • air moves out of the lungs down a pressure gradient
• what is pulmonary ventilation?

  the total volume of air that is moved into the lungs in one minute
• what is the equation for pulmonary ventilation?

  PV = tidal volume (dm3) x ventilation rate (min-1)
• what are the adaptations of the alveoli?

  Thin walls for quick diffusion due to short diffusion distance.

  Many of them providing a high surface area.

  Each alveoli are surrounded by capillaries, maintaining the concentration gradient.
• what are the parts of the gas exchange system in insects ?

  trachea, tracheoles, spiricles
• what are spiracles?

  round valve like openings along the abdomen of the insect where oxygen & CO2 enter and leave.

  • the trachea attach to these openings.
• what are the trachea in insects ?

  a network of internal tubes that have rings within them to strengthen them & keep them open.
• what are the tracheoles?

  many smaller tubes branching off from the trachea.

  • these deliver oxygen directly to respiring tissue.
• spiracles can open & close to prevent water loss.
• whats the structure of a fish gill?

  -gills are made up of stacks of gill filaments

  • each gill filament is covered in lamellae.
  • creating a large surface area.
• what are adaptations of gills ?

  thin diffusion distance due to capillary networks in the lamellae.

  maintaining the concentration gradients due to countercurrent flow.
• what is the countercurrent flow mechanism?

  when water flows over the gills in the opposite direction to the blood flow.

  • this ensures the equilibrium for oxygen concentration is never reached.
  • so the concentration gradient is always maintained across the gill length.
• what are the key structures of a leaf in gas exchange ?

  stomata

  palisade mesophyll (more densley packed)

  spongey mesophyll (has air spaces)
• whats an adaptation of plants to reduce water loss?

  stomata close
• what are adaptations of xerophytic plants to reduce water loss?

  curled leaves

  pitted stomata

  covered in hairs

  long roots to reach more water