structures in gaseous exchange system

• goblet cells - secrete mucus which traps microorganisms and dust particles in inhaled air, stops them reaching the alveoli
• cilia - beat the mucus, moves mucus upward away from the alveoli towards the throat, then swallowed. prevents lung infections
• elastic fibres - in walls of trachea, bronchi, bronchioles and alveoli

  • help process of breathing out
  • breathing in - the lungs inflate and elastic fibres are stretched. fibres then recoil to help push air out when exhaling
• smooth muscle - in the walls of trachea, bronchi and bronchioles

  • allows diameter to be controlled
  • during exercise it relaxes, making the tubes wider so there's less resistance to airflow and air can move in and out the lungs more easily
• rings of cartilage - in the walls of the trachea and bronchi

  • provide support and is strong and flexible and stops the bronchi and trachea from collapsing when you breathe in and the pressure drops
• complete table

  A) large c shaped pieces

  B) smaller pieces

  C) none

  D) none

  E) none

  F) none

  G) y

  H) y

  I) y

  J) y

  K) y

  L) y

  M) y

  N) y

  O) y

  P) y

  Q) y

  R) y

  S) n

  T) y

  U) n

  V) n

  W) y

  X) n