x

• What occurs in the process of inspiration?

  External intercostal muscles (while internal relax) and diaphragm muscles contract.

  This causes the ribcage to move upwards and outwards and the diaphragm to flatten, increasing the volume of the thorax.

  As the volume of the thorax increases, the lung pressure decreases.

  Thus air pressure outside the lungs is higher than the air pressure inside.

  This causes air to flow into the lungs to rebalance.

  Inspiration is an active process (it requires energy)
• What occurs in the process of expiration?

  The external intercostal muscles relax (while internal intercostal muscles contract) and diaphragm muscles relax.

  This causes the ribcage to move downwards and inwards and the diaphragm becomes curved again.

  The thorax volume decreases, causing the air pressure to increase to above atmospheric pressure.

  Air pressure inside the lungs is thus higher than the air pressure outside, so air moves out to rebalance.
• what happens in inspiration?


  external intercostal muscles contract

  diaphragm contracts and moves down

  ribcage moves upwards and outwards

  volume of thorax increases, causing lung pressure to decrease, creating a pressure gradient between outside the lungs and inside the lungs

  thus air flows inside the lungs down the pressure gradient

  air flows down the trachea into the alveoli
• what type of process is inspiration (breathing in)?


  active, as energy is required to power the muscle contraction (of external intercostal muscles and diaphragm)
• what happens in exhalation?


  the external intercostal muscles relax

  diaphragm relaxes and moves upwards

  internal intercostal muscles contract, moving the ribcage downwards and inwards

  the volume of the thorax decreases, increasing the pressure in the lungs

  creating a pressure gradient between outside the lungs and inside the lungs

  air flows out of the lungs down the pressure gradient, out of the alveoli and up the trachea