F211 - Exchange and Transport


The Lungs

Gaseuos exchange in the Lungs

  • oxygen passes from the air in the alevoli to the blood
  • carbon dioxide passes from the blood to the air in the alveoli  
  • ...by diffusion

How are the lungs adapted for exchange?

  • large surface area - more spcae for meolecules to pass through
  • a barrier permebable to oxygen and carbon dioxide
  • thin barrier to reduce diffusion pathway - alveolous one cell thick, capilary walls one cell thick
  • good blood supply - maintains a diffusion gradient as blood brings carbon dioxide(http://media1.shmoop.com/images/biology/biobook_animalmovement_graphik_38.png)
1 of 3



  • diaphram contracts and flattens puching the organs down
  • the intercoastal muscles contract raising the ribs
  • so the volume of the chest cavity increases
  • the pressure in the chest capity drop below the atmopsheric pressure
  • air moves into the lungs


  • diaphram relaxes and is pushed up by displaced organs underneath
  • intercoastla muscles relax and the ribs fall
  • so the volume of the chest cavity decreases
  • the pressure in the chest cavity inccreases above atmospheric pressure
  • air moves out of the lungs
2 of 3

Tissues in the Lungs

What are the functions of the tissues in the lung cells?


  • supports the trachea and bronchi by holding them open
  • prevents collapse when air pressure is low in inspiration
  • not a complete ring so there is some flexability so you can move your neck without restricting airways and so oesophagus can expand during swallowing

Smooth Muscle - can contract to restrict the airway to stop harmful substances entering alveoli

Elastic Fibres - when smooth muscle contracts the elastic fibres recoil to the original size to dilate the airways

Goblet cells and gladular tissue - secrete mucus to trap particles 

Ciliated epithilium - tiny hair like structures move to waft the muucus up the airway to the back of the throat

3 of 3


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Cellular processes and structure resources »